“It was also said, ‘Whoever divorces his wife, let him give her a certificate of divorce.’  But I say to you that everyone who divorces his wife, except on the ground of sexual immorality, makes her commit adultery, and whoever marries a divorced woman commits adultery.
 “Again you have heard that it was said to those of old, ‘You shall not swear falsely, but shall perform to the Lord what you have sworn.’  But I say to you, Do not take an oath at all, either by heaven, for it is the throne of God,  or by the earth, for it is his footstool, or by Jerusalem, for it is the city of the great King.  And do not take an oath by your head, for you cannot make one hair white or black.  Let what you say be simply ‘Yes’ or ‘No’; anything more than this comes from evil. (ESV)