Matthew 19:5-8

and said, 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. They say unto him, Why then did Moses command to give a bill of divorcement, and to put her away? He saith unto them, Moses for your hardness of heart suffered you to put away your wives: but from the beginning it hath not been so.