SHow me in the OT where God commanded anyone to take multiple wives.
In the NT Jesus clearly teaches against it.
The Gospel of Mark, And he arose from thence, and cometh into the coasts of Judaea by the farther side of Jordan: and the people resort unto him again; and, as he was wont, he taught them again.
Yet the whole family of Abraham came from plural Marriage from and Israel had the 12 tribes from Plural marriage.
Those at the time of Moses were living under the lesser law!
There is an event card in the scripture something like their is a scorce card in sports!
Sometimes it is at the beganning of a dispensation and other times the higher was with drawn and the people are living under the lesser law.
Without the standard works you might just lump all the events that are taking place under one umbrella.
As I stated before the Lord can employ or rescind the need of his ordinance.
If you are not aware of these laws there is no way you are going to miss them.
You will argue against them because you feel justified I am glad for the knowledge to understand why at certain times there was a need and a reason for plural marrige and other time it was not needed!