I find that, amidst today's insanity in the Church, this parable brings me some peace of mind. The following is from the Catena Aurea of St. Aquinas, on Mt. 13:24-30. Aquinas lays out the parable and then offers commentary on it by a variety of Fathers. See below, or the the actual page, if you prefer:

Catena Aurea, Mt. 13


24. Another parable put he forth to them, saying, The kingdom of heaven is likened to man which sowed good seed in his field:

25. But while men slept, his enemy came and sowed tares among the wheat, and went his way.

26. But when the blade was sprung up, and brought forth fruit, then appeared the tares also.

27. So the servants of the householder came and said to him, Sir, did you not sow good seed in your field; from whence then has it tares?

28. He said to them, An enemy has done this. The servants said to him, Will you then that we go and gather them up?

29. But he said, No; lest while you gather up the tares, you root up also the wheat with them.

30. Let both grow together until the harvest: and in the time of harvest I will say to the reapers, Gather together first the tares, and bind them in bundles to burn them: but gather the wheat into my barn.

CHRYS; In the foregoing parable the Lord spoke to such as do not receive the word of God; here of those who receive a corrupting seed. This is the contrivance of the Devil, ever to mix error with truth.

JEROME; He set forth also this other parable, as it were a rich householder refreshing his guests with various meats, that each one according to the nature of his stomach might find some food adapted to him. He said not 'a second parable,' but another; for had He said 'a second,' we could not have looked for a third; but another prepares us for many more.

REMIG; Here He calls the Son of God Himself the kingdom of heaven; for He said, The kingdom of heaven is like to a man that sowed good seed in his field.

CHRYS; He then points out the manner of the Devil's snares, saying, While men slept, his enemy came and sowed tares in the midst of the wheat, and departed. He here shows that error arose after truth, as indeed the course of events testifies; for the false prophets came after the Prophets, the false apostles after the Apostles, and Antichrist after Christ. For unless the Devil sees somewhat to imitate, and some to lay in wait against, he does not attempt any thing. Therefore because he saw that this man bears fruit an hundred, this sixty, and this thirty fold, and that he was not able to carry off or to choke that which had taken root, he turns to other insidious practices, mixing up his own seed, which is a counterfeit of the true, and thereby imposes upon such as are prone to be deceived. So the parable speaks, not of another seed, but of tares which bear a great likeness to wheat corn. Further, the malignity of the Devil is shown in this, that he sowed when all else was completed, that he might do the greater hurt to the husbandman.

AUG; He says, While men slept, for while the heads of the Church were abiding in sleep, and after the Apostles had received the sleep of death, then came the Devil and sowed upon the rest those whom the Lord in His interpretation calls evil children. But we do well to inquire whether by such are meant heretics, or Catholics who lead evil lives. That He says, that they were sown among the wheat, seems to point out that they were all of one communion. But forasmuch as He interprets the field to mean not the Church, but the world, we may well understand it of the heretics, who in this world are mingled with the good; for they who live amiss in the same faith may better be taken of the chaff than of the tares, for the chaff has a stem and a root in common with the grain. While schismatics again may be likened to ears that have rotted, or to straws that are broken, crushed down, and cast forth of the field. Indeed it is not necessary that every heretic or schismatic should be corporally severed from the Church; for the Church bears many who do not so publicly defend their false opinions as to attract the attention of the multitude, which when they do, then are they expelled. When then the Devil had sown upon the true Church diverse evil errors and false opinions; that is to say, where Christ's name had gone before, there he scattered errors, himself was the rather hidden and unknown; for He says, And went his way though indeed in this parable, as we learn from His own interpretation, the Lord may be understood to have signified under the name of tares all stumbling-blocks and such as work iniquity

CHRYS; In what follows He more particularly draws the picture of an heretic, in the words, When the blade grew, and put forth fruit, then appeared the tares also. For heretics at first keep themselves in the shade; but when, they have had long license, and when men have held communication with them in discourse, then they pour forth their venom.

AUG; Or otherwise; when a man begins to be spiritual, discerning between things, then he begins to see errors; for he judges concerning whatsoever he hears or reads, whether it departs from the rule of truth; but until he is perfected in the same spiritual things, he might be disturbed at so many false heresies having existed under the Christian name, whence it follows, And the servants of the householder coming to him said to him, Did you not sow good seed in your field? How then has it tares? Are these servants then the same as those whom He afterwards calls reapers? Because in His exposition of the parable, He expounds the reapers to be the Angels, and none would dare say that the Angels were ignorant who had sowed tares, we should the rather understand that the faithful are here intended by the servants. And no wonder if they are also signified by the good seed; for the same thing admits of different likenesses according to its different signification; as speaking of Himself He says that He is the door, He is the shepherd.

REMIG. They came to the Lord not with the body but with the heart and desire of the soul; and from Him they gather that this was done by the craft of the Devil, whence it follows, And he said to them, An enemy has done this.

JEROME; The Devil is called a man that is an enemy because he has ceased to be God; and in the ninth Psalm it is written of him, Up, Lord, and let not man have the upper hand. Wherefore let not him sleep that is set over the Church, lest through his carelessness the enemy should sow therein tares, that is, the dogmas of the heretics.

CHRYS; He is called the enemy on account of the losses he inflicts on men; for the assaults of the Devil are made upon us, though their origin is not in his enmity towards us, but in his enmity towards God.

AUG; And when the servants of God knew that it was the Devil who had contrived this fraud, whereby when he found that he had no power in open warfare against a Master of such great name, he had introduced his fallacies under cover of that name itself, the desire might readily arise in them to remove such men from out of human affairs if opportunity should be given them; but they first appeal to God's justice whether they should so do; The servants said, Will you that we go and gather them out?

CHRYS; Wherein observe the thoughtfulness and affection of the servants; they hasten to root up the tares, thus showing their anxiety about the good seed; for this is all to which they look, not that any should be punished, but that which is sown should not perish. The Lord's answer follows, And he said to them, No.

JEROME; For repentance is left, and we are warned that we should not hastily cut off a brother, since one who is today corrupted with an erroneous dogma, may grow wiser tomorrow, and begin to defend the truth; wherefore it is added, Lest in gathering together the tares you root out the wheat also.

AUG; Wherein He renders them more patient and tranquil. For this He says, because good men while yet weak, have need in some things of being mixed up with bad, either that they may be proved by their means, or that by comparison with them they may be greatly stimulated and drawn to a better course. Or perhaps the wheat is declared to be rooted up if the tares should be gathered out of it, on account of many who though at first tares would after become wheat; yet they would never attain to this commendable change were they not patiently endured while they were evil. Thus were they rooted up, that wheat which they would become in time if spared, would be rooted up in them. It is then therefore He forbids that such should be taken away out of this life, lest in the endeavor to destroy the wicked, those of them should be destroyed among the rest who would turn out good; and lest also that benefit should be lost to the good which would accrue to them even against their will from mixing with the wicked. But this may be done seasonably when, in the end of all, there remains no more time for a change of life, or of advancing to the truth by taking opportunity and comparison of others' faults; therefore He adds, Let both grow together until the harvest, that is, until the judgment.

JEROME; But this seems to contradict that command, Put away the evil from among you. For if the rooting up be forbidden, and we are to abide in patience till the harvest time, how are we to cast forth any from among us? But between wheat and tares (which in Latin we call 'lolium') so long as it is only in blade, before the stalk has put forth an ear, there is very great resemblance, and none or little difference to distinguish them by. The Lord then warns us not to pass a hasty sentence on an ambiguous word, but to reserve it for His judgment, that when the day of judgment shall come, He may cast forth from the assembly of the saints no longer on suspicion but on manifest guilt.

AUG; For when any one of the number of Christians included in the Church is found in such sin as to incur an anathema, this is done, where danger of schism is not apprehended, with tenderness, not for his rooting out, but for his correction. But if he be not conscious of his sin, nor correct it by penitence, he will of his own choice go forth of the Church and be separated from her communion; whence when the Lord commanded, Suffer both to grow together till the harvest, He added the reason, Saying, lest when you would gather out the tares you root up the wheat also. This sufficiently shows, that when that fear has ceased, and when the safety of the crop is certain, that is when the crime is known to all, and is acknowledged as so execrable as to have no defenders, or not such as might cause any fear of a schism, then severity of discipline does not sleep, and its correction of error is so much the more efficacious as the observance of love had been more careful. But when the same infection has spread to a large number at once, nothing remains but sorrow and groans. Therefore let a man gently reprove whatever is in his power; what is not so let him bear with patience, and mourn over with affection, until He from above shall correct and heal, and let him defer till harvest time to root out the tares and winnow the chaff. But the multitude of the unrighteous is to be struck at with a general reproof, whenever there is opportunity of saying anything among the people; and above all when any scourge of the Lord from above gives opportunity, when they feel that they are scourged for their deserts; for then the calamity of the hearers opens their ears submissively to the words of their reprover, seeing the heart in affliction is ever more prone to the groans of confession than to the murmurs of resistance. And even when no tribulation lays upon them, should occasion serve, a word of reproof is usefully spent upon the multitude; for when separated it is wont to he fierce, when in a body it is wont to mourn.

CHRYS; This the Lord spoke to forbid any putting to death. Or we ought not to kill an heretic, seeing that so a never-ending war would be introduced into the world; and therefore He says, Lest you root out with them the wheat also; that is, if you draw the sword and put the heretic to death, it must needs be that many of the saints will fall upon them. Hereby He does not indeed forbid all restraint upon heretics, that their freedom of speech should be cut off, that their synods and their confessions should put broken up - but only forbids that they should be put to death.

AUG; This indeed was at first my own opinion, that no man was to be driven by force into the unity of Christ; but he was to be led by discourse, tended with in controversy, and overcome by argument, we might not have men feigning themselves to be Catholic whom we knew to be declared heretics. But this opinion of mine was overcome not by the authority of those who contradicted me, but by the examples of those that showed it in fact; for the tenor of those laws in enacting which Princes serve the Lord in fear, has had such good effect, that already some say, This we desired long ago; but now thanks be to God who has made the occasion for us, and has cut off our pleas of delay. Others say, This we have long known to be the truth; but we were held by a kind of old habit, thanks be to God who has broken our chains Others again; We knew not that this was true, and had no desire to learn it, but fear has driven us to give our attention to it, thanks be to the Lord who has banished our carelessness by the spur of terror. Others, We were deterred from entering in by false rumors, which we should not bare known to be false had we not entered in, and we should not have entered in had we not been compelled; thanks be to God who has broken up our preaching by the scourge of persecution, and has taught us by experience how empty and false things lying fame had reported concerning His Church. Others say, We thought indeed that it was of no importance in what place we held the faith of Christ but thanks be to the Lord who has gathered us together out of our division, and has shown us that it is consonant to unity of God that He should be worshipped in unity. Let then the Kings of the earth show themselves the servants of Christ by publishing laws in Christ's behalf.

ID; But who is there of you who has any wish that a heretic should perish, nay, that he should so much as lose all? Could the house of David have had peace in no other war but by the death of Absalom in that war which he waged against his father; notwithstanding his father gave strict commands to his servants that they should save him alive and unhurt, that on his repentance there might be room for fatherly affection to pardon; what then remained for him but to mourn over him when lost, and to console his domestic affliction by the peace which it had brought to his kingdom Thus our Catholic mother the Church, when by the loss of a few she gains many, soothes the sorrow of her motherly heart, healing it by the deliverance of so much people. Where then is that which those are accustomed to cry out, That it is free to all to believe? Whom has Christ done violence to? Whom has He compelled? Let them take the Apostle Paul; let them acknowledge in him Christ first compelling and afterwards teaching; first smiting and afterwards comforting. And it is wonderful to see him who entered into the Gospel by the force of a bodily infliction laboring therein more than all those who are called by word only. Why then should not the Church constrain her lost sons to return to her, when her lost sons constrained others to perish?

REMIG; It follows, And in the time of harvest I will say to the reapers, Gather together first the tares, and bind them in bundles to burn them. The harvest is the season of reaping which here designates the day of judgment, in which the good are to be separated from the bad.

CHRYS; But why does He say, Gather first the tares? That the good should have no fears lest the wheat should be rooted up with them.

JEROME; In that He says that the bundles of tares are to be cast into the fire, and the wheat gathered into barns, it is clear that heretics also and hypocrites are to be consumed in the fires of hell, while the saints who are here represented by the wheat are received into the barns, that is into heavenly mansions.

AUG; It may be asked why He commands more than one bundle or heap of tares to be formed? Perhaps because of the variety of heretics differing not only from the wheat, but also among themselves, each several heresy, separated from communion with all the others, is designated as a bundle; and perhaps they may even then begin to be bound together for burning, when they first sever themselves from Catholic communion, and begin to have their independent church; so that it is the burning and not the binding into bundles that will take place at the end of the world. But were this so, there would not be so many who become wise again, and return from error into the Catholic Church. Wherefore we must understand the binding into bundles to be what shall come to pass in the end, that punishment should fall on them not promiscuously, but in due proportion to the obstinacy and willfulness of each separate error.

RABAN; And it should be noted that, when He says, Sowed good seed, He intends that good will which is in the elect; when He adds, An enemy came, He intimates that watch should be kept against him; when as the tares grow up, He suffers it patiently, saying, An enemy has done this, He recommends to us patience; when He says, Lest in gathering the tares, &c. He sets us an example of discretion; when hen He says, Suffer both to grow together till the harvest He teaches us long-suffering; and, lastly, He inculcates justice, when He says, Bind them into bundles to burn.