Removing the possibility of mending a marriage thus broken tended to prevent frivolous and impulsive divorces. The Pharisees asked Jesus concerning the Law of Moses related to divorce. Jesus told them that Moses permitted divorce and commanded the giving of a written bill of divorcement because of the hardness of their hearts. From this we learn first that it was God's intention that the home should be composed of one man and one woman, thus ruling out polygamy as part of the divine plan. The word adultery is used to describe illegitimate sex relations on the part of a married person.
Marriage is initiated by the private betrothal pledge.
The couple then comes forward to obtain the sanction of the state, and the Christian also to obtain the sanction of the church, by taking their vows before witnesses in the marriage ceremony. This is likely the exception to the rule given by our Lord. There would then be no exception for those who have legitimately become one flesh in consummation of their marriage vows. This exception clause was most important to the Jews who regarded betrothal vows to be as binding as we regard the marriage ceremony vows today. In Jesus' reply to the questions of the Pharisees, and in subsequent explanations to the disciples, He denied the right of man to legally annul the marriage bond and declared that the remarriage of either party constitutes adultery.