Do you think that the Law instructions would be enough?
"If he marries another woman, he must not deprive the first one of her food, clothing and marital rights."
Ex 21:10 NIV
"If a man has two wives, and he loves one but not the other, and both bear him sons but the firstborn is the son of the wife he does not love, when he wills his property to his sons, he must not give the rights of the firstborn to the son of the wife he loves in preference to his actual firstborn, the son of the wife he does not love."
Dt 21:15 NIV
- God was not concerned about having two wives nor about loving them equally, but about their sons...