Jesus taught monogamy. Matthew 19:9 and Mark 10:11-12: divorcing and marrying another = adultery, which wouldn't make sense if polygamy were permitted. 1 Timothy 3:2, 3:12, Titus 1:6: elders/deacons must be husband of one wife — referring to polygamy prohibition. 1 Corinthians 7:2-4: each man his own wife, each woman her own husband — mutual sexual exclusivity eliminates polygamy.

Matthew 19:9: marrying another after unjustified divorce = adultery. If polygamy were allowed, this wouldn't be adultery. Mark 10:11-12: same teaching, applied to both genders. 1 Timothy 3:2, 3:12, Titus 1:6: "husband of one wife" for elders/deacons — not requiring marriage (since Paul praised singleness) but prohibiting polygamy. 1 Corinthians 7:2-4: mutual exclusive sexual authority — wife has claim over husband's body AND husband over wife's — incompatible with polygamy.