Scripture

Mark 10:4
And they said, Moses suffered to write a bill of divorcement, and to put her away.
5 And Jesus answered and said unto them, For the hardness of your heart he wrote you this precept.
6 But from the beginning of the creation God made them male and female.
7 For this cause shall a man leave his father and mother, and cleave to his wife;
8 And they twain shall be one flesh: so then they are no more twain, but one flesh.