God made them Male and Female
what God has joined together, no human being must separate.

But Jesus told them, “Because of the hardness of your hearts he wrote you this commandment. But from the beginning of creation, ‘God made them male and female. For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh.’ So they are no longer two but one flesh.
Therefore what God has joined together, no human being must separate.”

Mark 10:5-9