God established the marriage law: "What God has joined together let no man put asunder" (Matthew 19:6). For at least three reasons He ordained the permanency of marriage:
1) Marriage is a type (or symbol) of the union between Christ and His church.
2) The love union between a man and his wife is God's way of establishing a home where children are born and raised for His glory.
3) A man and his wife may enjoy God together and help each other to carry out His will.
Many people consider God's law of marriage to be "unfair" as I have presented it, and many interpret it differently. But all of God's laws are for His glory and honor and for our ultimate joy and blessedness. Only sin and a hardened heart would try to make God's law different.