Tertullian

“ Gentile marriage, and him who was of old (that is, before marriage) a believer, that they should not be equally cautious for their flesh?—whereas the one is kept from marriage with an unbeliever, the other bidden to continue in it. Why, if we are defiled by a Gentile, is not the one disjoined, just as the other is not bound? ”

“ Gentile matrimony; according to the words themselves: “If,” it says, “any believer has an unbelieving wife;” it does not say, “takes an unbelieving wife.” It shows that it is the duty of one who, already living in marriage with an unbelieving woman, [3] has presently been by the grace of God converted, to continue with his wife; for this reason, to be sure, in order that no one, after attaining to faith, should think that he must turn away from a woman [4] who is now in some sense an “alien” and “stranger.” ”

“ If any of the brethren has an unbelieving wife, and she consents to the matrimony, let him not dismiss her; similarly, let not a believing woman, married to an unbeliever, if she finds her husband agreeable (to their continued union) , dismiss him: for the unbelieving husband is sanctified by the believing wife, and the unbelieving wife by the believing husband ”