You're being intentionally obtuse. How is this not approval?
Deuteronomy 21:15 If a man have two wives, one beloved, and another hated, and they have born him children, both the beloved and the hated; and if the firstborn son be hers that was hated: 21:16 Then it shall be, when he maketh his sons to inherit that which he hath, that he may not make the son of the beloved firstborn before the son of the hated, which is indeed the firstborn: 21:17 But he shall acknowledge the son of the hated for the firstborn, by giving him a double portion of all that he hath: for he is the beginning of his strength; the right of the firstborn is his.
What is it about "if a man have two wives" do you find challenging? Sheesh. Knock this off. As Christians we're supposed to be searching for the Truth. You're behaving like a liberal who's confronted with some reality that doesn't fit into a preconceived narrative.
Nor is there any mention of so-called “Natural Law” in the Bible;
Wrong again, Troll Folk.
Romans 2:14 For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves: 15 Which shew the work of the law written in their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another
The Natural Law contains the basic rules of morality that don't need Scripture for proof because they've already been "written our hearts" by God Himself. It's what C.S. Lewis called the "Tao." You don't need a Bible to tell you that stealing is wrong. That's the Natural Law. As St. Augustine put it:
Theft is surely punished by your law, O Lord, and by the law that is written in the human heart, the law that iniquity itself does not efface.
I really hope you are not ignoring Matthew 19:8 and Mark 10:5 here, especially the “hardness of the (Israelites’) hearts”. That applies to divorce and polygamy. Christians (especially the clerical leaders) are admonished to be the “husband of one wife” (1 Timothy 3:2, Titus 1:6; “mias gynaikos” means “one wife”). Cross-reference Deuteronomy 17:17.
If you are going to search for the truth, search for all of it. Man has to live by every word of God, omitting nothing and adding nothing to it. The phrase “every man did that which was right in his own eyes” is in the book of Judges twice, as a warning to us.
And Romans 2:14 has nothing to do with the pagan concept of “natural law”. The Greek word “phusei” (literally “growth”) used here refers to a habit or custom passed on from generation to generation, which is taught rather than innate.
Uh...
Assuming that the phrase "at the same time" is missing?