Canon XVII
If any woman from pretended asceticism shall cut off her hair, which God gave her as the reminder of her subjection, thus annulling as it were the ordinance of subjection, let her be anathema.
Ancient Epitome of Canon XVII.
Whatever women shave their hair off, pretending to do so out of reverence for God, let them be anathema.
The apostle Paul, in the 1 Cor. 11.10, represents the long hair of women, which is given them as a natural veil, as a token of their subjection to man. We learn from the Synod of Gangra, that as many Eustathian women renounced this subjection, and left their husbands, so, as this canon says, they also did away with their long hair, which was the outward token of this subjection. An old proverb says: duo si faciunt idem, non est idem. In the Catholic Church also, when women and girls enter the cloister, they have their hair cut off, but from quite other reasons than those of the Eustathian women. The former give up their hair, because it has gradually become the custom to consider the long hair of women as a special beauty, as their greatest ornament; but the Eustathians, like the ancient Church in general, regarded long hair as the token of subjection to the husband, and, because they renounced marriage and forsook their husbands, they cut it off.
This canon is found in the Corpus Juris Canonici, Gratian’s Decretum, Pars I., Dist. xxx., c. ij.