Matthew 5:31 says, It hath been said, Whosoever shall put away his wife, let him give her a writing of divorcement:  Divorce was allowed in the Old Testament, and it was very much at the discretion of the husband.  The letter of the law required that he give his wife a writing of divorcement.  This was a legal situation and not a spiritual one.  Under God's law, marriage is intended to be a spiritual union between a man and a woman that would last a lifetime.  We have made it a legal institution that lasts as long as it is convenient.  Verse thirty-two declares, But I say unto you, That whosoever shall put away his wife, saving for the cause of fornication, causeth her to commit adultery: and whosoever shall marry her that is divorced committeth adultery.  Unless the divorce was based on adultery, then the spirit of God's law says that if a woman, in this case, is divorced and remarries, both she and her new husbands are guilty of adultery.  The same applies to the wife.  Often today people get divorced simply because they want to get remarried.  I believe that the real problem with marriage today is that it has become simply a legal institution instead of a spiritual one.  Verse thirty-three states, Again, ye have heard that it hath been said by them of old time, Thou shalt not forswear thyself, but shalt perform unto the Lord thine oaths:  Matthew Henry says this refers to taking oaths to tell the truth.  We are not to swear by our own merit, but by our faith in and relationship to God.  This is the letter of the law.  Verse thirty-four states, But I say unto you, Swear not at all; neither by heaven; for it is God’s throne:  In this verse we begin to get into the spirit of the law.  This does not mean that we are never to swear an oath, but that the oath is not to be based on material things, but on our relationship with God.  Everything already belongs to God.  Heaven is God's thorn.  Verse thirty-five says, Nor by the earth; for it is his footstool: neither by Jerusalem; for it is the city of the great King.  The earth is God's footstool and Jerusalem is His city, so how can we swear by, or take an oath, based on any of these things.  For our oaths to have any real meaning, they must be based on our relationship with God.  Verse thirty-six states, Neither shalt thou swear by thy head, because thou canst not make one hair white or black.  Now we might say that we can make our hair white or black or even purple, but we really can't.  We can make it appear that way, but at the root it is still the same color.  That being said, I believe that we are being advised to not swear by our own merit or values.  As followers of Christ, God should be in control of every aspect of our lives.  Verse thirty-seven says, But let your communication be, Yea, yea; Nay, nay: for whatsoever is more than these cometh of evil.  I believe this means that we should be truthful in what we say.  If we say yes to someone, it should not mean maybe, and the same is true if we say no.