By St. Gregory the Theologian
"The two", He says, "shall be one flesh" (Gen. 2:23); so let the one flesh have equal honour. And Paul legislates for chastity by His example. How, and in what way? "This Mystery is great", he says, "but I speak concerning Christ and the Church" (Eph. 5:32). It is well for the wife to reverence Christ through her husband: and it is well for the husband not to dishonor the Church through his wife. Let the wife, he says, see that she reverence her husband, for so she does Christ; but also he bids the husband cherish his wife, for so Christ does the Church. Let us, then, give further consideration to this saying.
On Divorce and Remarriage
"Churn milk and it will be butter" (Prov. 30:33); examine this and perhaps you may find something more nourishing in it. For I think that the word here seems to deprecate second marriage. For, if there were two Christs, there may be two husbands or two wives; but if Christ is One, one Head of the Church, let there be also one flesh, and let a second be rejected; and if it hinder the second what is to be said for a third? The first is law, the second is indulgence, the third is transgression, and anything beyond this is swinish, such as has not even many examples of its wickedness. Now the Law grants divorce for every cause; but Christ not for every cause; but He allows only separation from the whore; and in all other things He commands patience. He allows to put away the fornicatress, because she corrupts the offspring; but in all other matters let us be patient and endure; or rather be enduring and patient, as many as have received the yoke of matrimony. If you see lines or marks upon her, take away her ornaments; if a hasty tongue, restrain it; if a merry laugh, make it modest; if immoderate expenditure or drink, reduce it; if unseasonable going out, shackle it; if a lofty eye, chastise it. It is uncertain which is in danger, the separator or the separated. "Let your fountain of water", it says, "be only your own, and let no stranger share it with you" (Prov. 5:17); and, let the colt of your favours and the stag of your love company with you; do thou then take care not to be a strange river, nor to please others better than your own wife. But if you be carried elsewhere, then you make a law of lewdness for your partner also. Thus says the Saviour.
From Oration 37.