(1)  I believe Polygamy was not a sin under the Old Covenant. 

(2) I believe Polygamy is a sin under the New Covenant. 

I would assume all on this list would agree with me on point (2) and most, not all, would agree with point (1).

Questions: 
One:  If any believe Polygamy was indeed a sin under the Old Covenant, upon what Scriptures do you base that view. 

Two: If you believe Polygamy was not a sin under the Old Covenant but it is a sin under the New Covenant, what NTS do you use to prove that it is now a sin?

The answers to these question involve the validity of one the three major, and essential, maxims of Covenant Theology.

JGR