Matthew 19:4-6
King James Version
4 And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female,

5 And said, For this cause shall a man leave father and mother, and shall cleave to his wife: and they twain shall be one flesh?

6 Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder.