matthew 5:31 It hath been said, Whosoever shall put away his wife, let him give her a writing of divorcement: - Free Bible Online

      31. It hath been said--This shortened form was perhaps intentional, to mark a transition from the commandments of the Decalogue to a civil enactment on the subject of divorce, quoted from De 24:1. The law of divorce--according to its strictness or laxity--has so intimate a bearing upon purity in the married life, that nothing could be more natural than to pass from the seventh commandment to the loose views on that subject then current.
      Whosoever shall put away his wife, let him give her a writing of divorcement--a legal check upon reckless and tyrannical separation. The one legitimate ground of divorce allowed by the enactment just quoted was "some uncleanness"--in other words, conjugal infidelity. But while one school of interpreters (that of SHAMMAI) explained this quite correctly, as prohibiting divorce in every case save that of adultery, another school (that of HILLEL) stretched the expression so far as to include everything in the wife offensive or disagreeable to the husband--a view of the law too well fitted to minister to caprice and depraved inclination not to find extensive favor. And, indeed, to this day the Jews allow divorces on the most frivolous pretexts. It was to meet this that our Lord uttered what follows:

JFB.