Genesis 2:24
For this reason a man will leave his father and mother and be united to his wife, and they will become one flesh.

Matthew 19:4-6
“Haven’t you read,” he replied, “that at the beginning the Creator ‘made them male and female, and said, ‘For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh. So they are no longer two, but one. Therefore what God has joined together, let man not separate.”