GEN349 Polygamy, though not expressly forbidden in the Torah, is mentioned as the cause which turns the hearts of kings away from the true worship of God. It is to be eschewed as a potential danger to the peaceful married life. [this verse, where the words “and he shall cleave until his wife”, explicitly show that man is to possess only one wife at a time.]  Maimonides, in the special section dealing with forbidden sexual relationships, Mishneh Torah, Issure Biah 17:13, deduces from the command to the High Priest “And he shall take a wife in her virginity” Leviticus 21:13, that even he was allowed to marry only one wife at a time. … Nothing must be done to endanger the holy alliance (Kiddushin) of man and wife.  The Rabbis devote five tractates of the Talmud to this theme. Kiddushin and Ketubot deal mainly with marriage settlements; Yebamot [Yevamot] with Levirate and prohibited marriages; Sotah with the woman suspected of adultery and Gittin with divorce, not to mention the references to these themes scattered over the other tractates. The Rabbis found it necessary to deal with these themes exhaustively in view of the vagueness of the Biblical laws. These Talmudic views have been systemically collected in two works that are still the authoritative sources of every Rabbi. These are the Mishneh Torah of Maimonides and the Eben Ha’ezer of Joseph Karo [i.e. second section of his Shulchan Aruch - AJL]  [No fewer than one hundred and seventy-eight sections dealing with marriage and divorce appear in Karo’s work].  These authorities warn that intermarriage is likely to mar family purity and sow dissension and produce disreputable children. Deuteronomy 7:3-4; Ezra 9:1-2, 10:1-11; Nehemiah 10:31, 13:23-25; Avodah Zara 31b; Eben Ha’ezer 16:1; Maimonides Issure Biah 12:1.  Though one Rabbinic view states that “Gentiles in the Diaspora cannot really be termed idolaters”, yet marriage with them is disallowed. Chullin 13b.  Underlying all these restrictions is the ethical contention that just as virtue and righteousness flow from the worship of God, so do vice and oppression issue from the ungodly marriage, especially with daughters of the heathen. This will explain the seemingly harsh measures taken, especially by Ezra, against idolatry and immorality, both of which are to be eliminated. Exodus 20:3; Leviticus 19:4; Deuteronomy 4:15-25.  A “holy people” must remove all obstacles to the purity of family life and regard them as abominations. Deuteronomy 7:3 Marriage is something more than a civil contract; it is an institution based on morality and implying the most sacred duties. It was wrong for one to betroth a wife before he had seen her Kiddushin 41a or to marry a partner much younger or much older than himself. Yevamot 101b. In either case, the main object of marriage, procreation, would be jeopardized on account of age and impotency.  LEHRMAN 241-2