Catena Aurea on Matthew 19:9: Augustine of Hippo

For a reunion of the wedlock, even after actual commission of adultery, is neither shameful nor difficult, where there is an undoubted remission of sin through the keys of the kingdom of heaven; not that after being divorced from her husband an adulteress should be called back again, but that after her union with Christ she should no longer be called an adulteress.