Read full article
Genesis 29:30-33 shows God being concerned about ONE man not loving TWO wives. God acts on this concern by helping the two wives become impregnated by the ONE and same man.
Now remember, all that God does is morally good so His concerns and actions not only show what he wants or accepts, but also counts towards what’s morally good. The logical implications of Genesis 29:30-33 is that it’s moral for ONE man to love and impregnate TWO women.
The 10 commandments clearly list ‘adultery’ is being a sin, something which man is not to do. The rules on adultery were enforced before (in Genesis) and after the law was given to Moses (Exodus and beyond). So there was never a concession for adultery.
If polygamy was wrong it would be the sin of adultery. Yet not one man who married multiple unmarried woman was judged to be an adulterer. Therefore, polygamy was not a sin.
Both lines of evidence not only show that polygamy was not a sin, but also that God directly intervened in such relationships to facilitate them rather than breaking them up or punishing them.