Let the husband not be insolent nor arrogant towards his wife; but compassionate, bountiful, willing to please his own wife alone, and treat her honourably and obligingly, endeavouring to be agreeable to her; (III.) not adorning yourself in such a manner as may entice another woman to you. For if you are overcome by her, and sinnest with her, eternal death will overtake you from God; and you will be punished with sensible and bitter torments. Or if you do not perpetrate such a wicked act, but shakest her off, and refusest her, in this case you are not wholly innocent, even though you are not guilty of the crime itself, but only in so far as through your adorning you enticed the woman to desire you. For you are the cause that the woman was so affected, and by her lusting after you was guilty of adultery with you: yet are you not so guilty, because you did not send to her, who was ensnared by you; nor did you desire her. Since, therefore, you did not deliver up yourself to her, you shall find mercy with the Lord your God, who has said, "You shall not commit adultery," and, "You shall not covet." For if such a woman, upon sight of you, or unseasonable meeting with you, was smitten in her mind, and sent to you, but you as a religious person refused her, if she was wounded in her heart by your beauty, and youth, and adorning, and fell in love with you, you will be found guilty of her transgressions, as having been the occasion of scandal to her, Matthew 18:7 and shall inherit a woe. Wherefore pray to the Lord God that no mischief may befall you upon this account: for you are not to please men, so as to commit sin; but God, so as to attain holiness of life, and be partaker of everlasting rest. That beauty which God and nature has bestowed on you, do not further beautify; but modestly diminish it before men. Thus, do not permit the hair of your head to grow too long, but rather cut it short; lest by a nice combing your hair, and wearing it long, and anointing yourself, you draw upon yourself such ensnared or ensnaring women. Neither do you wear over-fine garments to seduce any; neither do you, with an evil subtlety, affect over-fine stockings or shoes for your feet, but only such as suit the measures of decency and usefulness. Neither do you put a gold ring upon your fingers; for all these ornaments are the signs of lasciviousness, which if you be solicitous about in an indecent manner, you will not act as becomes a good man: for it is not lawful for you, a believer and a man of God, to permit the hair of your head to grow long, and to brush it up together, nor to suffer it to spread abroad, nor to puff it up, nor by nice combing and platting to make it curl and shine; since that is contrary to the law, which says thus, in its additional precepts: "You shall not make to yourselves curls and round rasures." Nor may men destroy the hair of their beards, and unnaturally change the form of a man. For the law says: "You shall not mar your beards." For God the Creator has made this decent for women, but has determined that it is unsuitable for men. But if you do these things to please men, in contradiction to the law, you will be abominable with God, who created you after His own image. If, therefore, you will be acceptable to God, abstain from all those things which He hates, and do none of those things that are unpleasing to Him.http://www.newadvent.org/fathers/07151.htm
Does this still apply? Scary!
And, didn't Jesus Himself had long hair? How then is it forbidden for men to have long hair?