It appears to me that divorce is legitimate when the contract of “one flesh” is abandoned, in which case both parties are free of the former two-party contract.  Or if one party who is an unbeliever does not want to make a commitment and is prone to leave, 1 Cor. 7.   Multiple wives do not make for a divorce, thus for King David and Solomon divorce from them was not legitimate which makes defining these things confusing.

Jesus answers the Pharisees in Matthew 19 that a man can not divorce his wife for any reason, and they who divorce for any reason not only commit adultery but make their spouse commit adultery.  If one party in a Christian marriage has left the duty of marriage they in effect have left the duty to others and both are responsible for adultery.  However, Moses in old time had allowed divorce due to the hardness of men’s hearts possibly to go beyond fornication to some degree.  So it has been and is permissible but not for any reason other than adultery and fornication from the way I see it.

Matthew 19 reads as follows:

19 And it came to pass, that when Jesus had finished these sayings, he departed from Galilee, and came into the coasts of Judaea beyond Jordan; And great multitudes followed him; and he healed them there. The Pharisees also came unto him, tempting him, and saying unto him, Is it lawful for a man to put away his wife for every cause? And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female, And said, For this cause shall a man leave father and mother, and shall cleave to his wife: and they twain shall be one flesh? Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder. They say unto him, Why did Moses then command to give a writing of divorcement, and to put her awayHe 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. And I say unto you, Whosoever shall put away his wife, except it be for fornication, and shall marry another, committeth adultery: and whoso marrieth her which is put away doth commit adultery. 10 His disciples say unto him, If the case of the man be so with his wife, it is not good to marry. 11 But he said unto them, All men cannot receive this saying, save they to whom it is given. 12 For there are some eunuchs, which were so born from their mother’s womb: and there are some eunuchs, which were made eunuchs of men: and there be eunuchs, which have made themselves eunuchs for the kingdom of heaven’s sake. He that is able to receive it, let him receive it.

Here we read “Whomever shall put away his wife, except for it be for fornication, and shall marry another, committeth adultery: and whoso marrieth her which is put away doth commit adultery.”  Some people interpret here that because only “put away” is here in the text without “writing of divorcement” that the subject of Matthew 19 has to do with those who “put away” their wives without the paper making it legal.  However Jesus Himself uses only “put away” to speak of a full divorce.  Furthermore, the subject is divorce not how to do a legal righteous divorce.  The subject is what God has joined together let man not separate it.

Therefore, there is no such thing as a clear case for divorce, unless one of the parties is not a Christion or there is adultery.  Matthew could read “Whoever shall put away his wife for adultery (or because she has left the marriage as an unbeliever 1 Cor. 7) and shall marry another does not commit adultery.”  But if that is the case why does 10b say ” and whoso marrieth her which is put away doth commit adultery.”?  In this case, I could see why someone could argue that “put away” herein 10b only refers to a partial divorce.  If it was a completely legitimate divorce how could the guilty party be guilty of adultery two times?