First, I want to say that marriage is an institution of God given to man. It was not given to Adam as an individual, or to him and Eve as a pair. It was given to man, and they were the first to enjoy its blessed provisions. “Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one flesh” (Gen. 2:24). That this applies to man generally is true because strictly it was not true of Adam; He did not leave his father and his mother to cleave unto Eve, but man generally does so have to do. Since marriage is for men generally and universally, we conclude that the law regulating the institution is for all man. It is a mistake to think the laws of marriage only apply to people in the church, and not people of the world. If the laws regulating marriage are binding only on the church members, it would follow that God does not join in matrimony those who are not Christians. Marriage is not a church ordinance. Marriage did not begin on the day of Pentecost; it began with Adam and Eve.
In Matthew 19:3, the Pharisees came to Jesus, they came testing Him, tempting Him. These Pharisees asked Jesus, “Is it lawful for a man to divorce his wife for just any reason?” The Lord's response: “And he answered and said, Have ye not read, that he who made (them) from the beginning made them male and female, and said, For this cause shall a man leave his father and mother, and shall cleave to his wife; and the two shall become one flesh? So that they are no more two, but one flesh. What therefore God hath joined together, let not man put asunder” (Matt. 19:4-6). Jesus settled the question by the original design of marriage, as shown in Gen. 2:24. The Pharisees asked the Lord; in view of His answer that there is to be no break in a marriage, “Why then did Moses command to give a bill of divorcement, and to put (her) away?” (Matt. 19:7). They are saying you have to be wrong because you are contradicting Moses in Deuteronomy 24. Jesus answered this question by saying; “Moses for your hardness of heart suffered you to put away your wives: but from the beginning it hath not been so” (Matt. 19:8). Notice, first of all, that the Pharisees had interpreted Deuteronomy 24:1-4 as a command (Matt. 19:7), but Jesus corrects that in this verse by implying that Moses didn't command divorce; he rather permitted, allowed, and suffered it. God permitted this, says Jesus, because of your hardness of heart. This was not God's original intention; from the beginning it has not been this way. In other words, God's law about marriage had never been taken away. God had only granted through Moses a temporary exemption from its observance. This is extremely important to keep in mind as one evaluates the claims of certain people who maintain that Matthew 19:9 is a covenant passage and therefore limited in application to those who are already members of the church. Since Jesus' teaching in Matthew 19:9 is designed to reaffirm Jehovah's original marriage code; the verse cannot be so-called covenant passage, that it only applies to a Christian husband and wife. Christ's teaching on marriage was a restoration of heaven's original plan. But God's original plan surrounded mankind as a whole. Thus, Christ's teaching on marriage surrounded mankind as a whole. He will restore marriage to the level of the Father's original intention.
“And I say unto you, Whosoever shall put away his -wife, except for fornication, and shall marry another, committeth adultery: and he that marrieth her when she is put away committeth adultery” (Matt. 19:9). “Whosoever”, meaning any one, that is, this teaching is not limited to just members of the church; it applies to whatever man divorces in the manner Jesus described, “fornication”. Fornication indicates the one reason for which a person might divorce a mate and remarry and still be innocent before God. Anyone who holds there is some other door than the one named by Jesus holds that Jesus did not tell truth! Whoso, that is, what ever person marries the woman put away by her husband, whether the reason was fornicating or because she burned the bread, doth commit adultery, because she is not marriageable in either case. The Lord had stressed that there is one scriptural ground upon which there can be divorced and remarriage acceptable to God. This, the cause of fornication! To the disciples this was a hard saying (Matt. 19:10).
It is alleged by some that since baptism washes away all sins (Acts 22:16), it sanctifies marriages which existed at the time of baptism - so - those involved in adulterous marriages (Those which violate Matthew 19:9) do not have to separate after baptism. They say baptism sanctifies a sinful relationship. Baptism does not destroy a sinful marriage and create a righteous one. Repentance is before baptism. Repentance demands a reformation of life. In the case of an unscriptural marriage (one which violates Matt. 19:9), repentance demands that one get out of that marriage. If a man has stolen a horse, if he truly repents, he will not keep the horse. Suppose a man is living in polygamy, and he decides to obey the gospel: May he continue to live with a dozen wives after his repentance and baptism? Does his obedience to these commandments of the gospel change his polygamy from unholy relations to holy relations? Polygamy is one form of adultery; living with a person who has been divorced from another for any cause except fornication is another form of adultery. Repentance means that one ceases to live in sin. The thief quits stealing when he repents, and the one living in adultery with a divorcee must dissolve his adulterous union.
Divorce for any cause than fornication does not destroy the union in God's sight. “What God joined, no man can put asunder”. Since God joins a man to his first lawful wife and since divorce for trivial cause does not destroy that union, if the man marries he is living with one woman while bound to another. That is what makes the second union unholy. Baptism does not change the nature of that union. Jesus taught that fornication was the only cause whereby one could dissolve the marriage bond and be eligible to remarry.