matthew 19:8 He saith unto them, Moses because of the hardness of your hearts suffered you to put away your wives: but from the beginning it was not so. - Free Bible Online

      8. He saith unto them, Moses--as a civil lawgiver.
      because of--or "having respect to."
      the hardness of your hearts--looking to your low moral state, and your inability to endure the strictness of the original law.
      suffered you to put away your wives--tolerated a relaxation of the strictness of the marriage bond--not as approving of it, but to prevent still greater evils.
      But from the beginning it was not so--This is repeated, in order to impress upon His audience the temporary and purely civil character of this Mosaic relaxation.

JFB.