Other than for church leaders, where does the Bible speak out against polygamy?
Ephesians 5:31. Unambiguous. All other verses of that chapter in context show a marriage of one man and one woman, not limited to church leaders.
That’s aside from the example in Genesis 2:24, where God gave Adam one wife, not multiple wives. Noah also had one wife, as did his three sons have one wife each.
Also the injunction is made specially for kings, not to marry many wives, in Deuteronomy 17:17. (The later examples of David and Solomon, especially Solomon, show what happen when that’s ignored.)
AHHhhh...
The Catholic mindset appears:
IF the bible does NOT speak against it; then why CAN'T we do it?
Are not ALL things possible with GOD?
...cleave to his WIFE - not WIVES.