If a man has two wives, one beloved, and another hated, and they have borne him children, both the beloved and the hated; and if the firstborn son be hers that was hated:
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Ambrose of Milan
Since that discourse took up an example from Deuteronomy for its assertion, where it is connected with “the man who had two wives, one hateful, the other lovable,” it is not unreasonable for you to be concerned, lest someone should perhaps think that the passage advocated that the man had two souls. This is not at all possible. Truly, you yourself are not unaware that sometimes when Scripture speaks allegorically, one thing refers to the form of the synagogue, another to the church. One thing refers to the soul, another to the mystery of the Word and another to different forms and qualities of souls which the spiritually discerning person recognizes. In the following chapter of the law I judge that not two souls but different qualities of one soul were meant. For there is the form of the lovable soul, which delights in pleasures, flees from labor, shuns compunction and rejects the judgment of God. It is lovable in this way: it seems sweet and agreeable at the time. This form of the sou...
Two wives. Moses never expressly (Haydock) sanctions polygamy; but he tolerates it frequently, as excused by custom, the example of the Patriarchs; a toleration which Christ has revoked, as contrary to the primary design of God, and the institution of matrimony. (Calmet) (Matthew xix.)