What is marriage? God made man in the image of God, male and female he made them. This means that we see a picture of God through man most through marriage, the joining of man and woman to be one flesh. When a man leaves his father and mother and cleaves to his wife, the two become one flesh, which is a joining together by God. God says that this “one flesh” union is to be permanent here on earth – what God has joined together let not man separate.
Several reasons are given for this one flesh relationship. God is relational and he desires for his creation to live in relationship – marriage being the apex of this relationship. God saw that man was alone and it was not good – so marriage is to bring companionship rather than aloneness. Also, for the sake of the children that will come from this union, having a more complete picture of God – whose image is male and female – children need to see and draw this benefits from this union. God reveals himself to children first through this union properly working as he created them husbands and wives to be one.
Scripture references: Genesis, Malachi, and gospels.