I find Aquinas helpful in understanding our Lord's human frailty:
Article 1. Whether the Son of God in human nature ought to have assumed defects of body?
Objection 1. It would seem that the
Son of God ought not to have assumed
human nature with defects of body. For as His
soul is personally united to the
Word of God, so also is His body. But the
soul of
Christ had every perfection, both of
grace and
truth, as was said above (
III:7:9;
9, seqq.). Hence, His body also ought to have been in every way perfect, not having any imperfection in it.
Objection 2. Further, the
soul of
Christ saw the
Word of God by the vision wherein the blessed see, as was said above (
III:9:2), and thus the
soul of
Christ was blessed. Now by the beatification of the
soul the body is glorified; since, as
Augustine says (Ep. ad Dios. cxviii), "
God made the
soul of a
nature so strong that from the fulness of its blessedness there pours over even into the lower
nature" (i.e. the body), "not indeed the bliss proper to the beatific fruition and vision, but the fulness of health" (i.e. the vigor of incorruptibility). Therefore the body of
Christ was incorruptible and without any defect.
Objection 3. Further, penalty is the consequence of fault. But there was no fault in
Christ, according to
1 Peter 2:22: "Who did no guile." Therefore defects of body, which are penalties, ought not to have been in Him.
Objection 4. Further, no reasonable
man assumes what keeps him from his proper end. But by such like bodily defects, the end of
Incarnation seems to be hindered in many ways. First, because by these infirmities men were kept back from
knowing Him, according to
Isaiah 53:2-3: "[There was no sightliness] that we should be desirous of Him. Despised and the most abject of
men, a man of sorrows and acquainted with infirmity, and His look was, as it were, hidden and despised, whereupon we esteemed Him not." Secondly, because the de. sire of the Fathers would not seem to be fulfilled, in whose
person it is written (
Isaiah 51:9): "Arise, arise, put on Thy strength, O Thou Arm of the Lord." Thirdly, because it would seem more fitting for the
devil's power to be overcome and
man's weakness healed, by strength than by weakness. Therefore it does not seem to have been fitting that the
Son of God assumed
human nature with infirmities or defects of body.
On the contrary, It is written (
Hebrews 2:18): "For in that, wherein He Himself hath suffered and been tempted, He is able to succor them also that are tempted." Now He came to succor us. hence David said of Him (
Psalm 120:1): "I have lifted up my eyes to the mountains, from whence help shall come to me." Therefore it was fitting for the
Son of God to assume flesh subject to
human infirmities, in order to suffer and be tempted in it and so bring succor to us.
I answer that, It was fitting for the body assumed by the
Son of God to be subject to
human infirmities and defects; and especially for three reasons. First, because it was in order to satisfy for the
sin of the
human race that the
Son of God, having taken flesh, came into the world. Now one satisfies for another's
sin by taking on himself the punishment due to the
sin of the other. But these bodily defects, to wit, death, hunger, thirst, and the like, are the punishment of
sin, which was brought into the world by
Adam, according to
Romans 5:12: "By one
man sin entered into this world, and by
sin death." Hence it was useful for the end of
Incarnation that He should assume these penalties in our flesh and in our stead, according to
Isaiah 53:4, "Surely He hath borne our infirmities." Secondly, in order to
cause belief in
Incarnation. For since
human nature is
known to
men only as it is subject to these defects, if the
Son of God had assumed
human nature without these defects, He would not have seemed to be
true man, nor to have
true, but
imaginary, flesh, as the Manicheans held. And so, as is said,
Philippians 2:7: "He . . . emptied Himself, taking the form of a servant, being made in the likeness of
men, and in
habit found as a man." Hence, Thomas, by the sight of His wounds, was recalled to the
faith, as related
John 20:26. Thirdly, in order to show us an example of patience by valiantly bearing up against
human passibility and defects. Hence it is said (
Hebrews 12:3) that He "endured such opposition from sinners against Himself, that you be not wearied. fainting in your minds."
Reply to Objection 1. The penalties one suffers for another's
sin are the
matter, as it were, of the satisfaction for that
sin; but the principle is the
habit of
soul, whereby one is inclined to wish to satisfy for another, and from which the satisfaction has its efficacy, for satisfaction would not be efficacious unless it proceeded from
charity, as will be explained (
Supplement:14:2). Hence, it behooved the
soul of
Christ to be perfect as regards the
habit of
knowledge and
virtue, in order to have the power of satisfying; but His body was subject to infirmities, that the
matter of satisfaction should not be wanting.
Reply to Objection 2. From the
natural relationship which is between the
soul and the body,
glory flows into the body from the
soul's glory. Yet this
natural relationship in
Christ was subject to the
will of His Godhead, and thereby it came to pass that the beatitude remained in the
soul, and did not flow into the body; but the flesh suffered what belongs to a passible
nature; thus
Damascene says (De Fide Orth. iii, 15) that, "it was by the consent of the Divine will that the flesh was allowed to suffer and do what belonged to it."
Reply to Objection 3. Punishment always follows
sin actual or original, sometimes of the one punished, sometimes of the one for whom he who suffers the punishment satisfies. And so it was with
Christ, according to
Isaiah 53:5: "He was wounded for our iniquities, He was bruised for our
sins."
Reply to Objection 4. The infirmity assumed by
Christ did not impede, but greatly furthered the end of
Incarnation, as above stated. And although these infirmities concealed His Godhead, they made
known His Manhood, which is the way of coming to the Godhead, according to
Romans 5:1-2: "By
Jesus Christ we have access to
God." Moreover, the ancient Fathers did not desire bodily strength in
Christ, but
spiritual strength, wherewith He vanquished the
devil and healed
human weakness.