Matthew 19:4–6
4 And He answered and said to them, “Have you not read that He who made them at the beginning‘made them male and female,’ 5 and said, ‘For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh’ ? 6 So then, they are no longer two but one flesh. Therefore what God has joined together, let not man separate.”
Leviticus 18:22 You shall not lie with ra male as with a woman. It is an abomination.
Romans 1:26–27
26 For this reason God gave them up to vile passions. For even their women exchanged the natural use for what is against nature. 27 Likewise also the men, leaving the natural use of the woman, burned in their lust for one another, men with men committing what is shameful, and receiving in themselves the penalty of their error which was due.
Genesis
God made the first man and woman—the first marriage. Thus, marriage can only be a man and a woman because we are accountable to the One who made marriage in the first place. And don’t forget—according to Scripture, one of the primary reasons for marriage is to produce godly offspring.11 Adam and Eve were told to be fruitful and multiply, but there’s no way a gay marriage can fulfill this command!