Tertullian (Rome, 160 - 220), To His Wife, Bk. 2:7, ML 1, 1299
If, then, a
marriage of this kind (faithful with unfaithful) is
approved by God, why will it not also be a
successful marriage,
in spite of difficulties and anxieties and obstacles
and
defilements, since it already enjoys the patronage
of Divine
grace, at least in part?