Mark 10:5-12

But Jesus said unto them, For your hardness of heart he wrote you this commandment. But from the beginning of the creation, Male and female made he them. For this cause shall a man leave his father and mother, and shall cleave to his wife; and the two shall become one flesh: so that they are no more two, but one flesh. What therefore God hath joined together, let not man put asunder. And in the house the disciples asked him again of this matter. And he saith unto them, Whosoever shall put away his wife, and marry another, committeth adultery against her: and if she herself shall put away her husband, and marry another, she committeth adultery.