For this reason a man will leave his father and mother and be united to his wife, and they will become one flesh. Genesis 2:24

From the beginning of all human time - Adam and Eve - God instituted the idea of a man and a woman coming together to complete a relationship. God saw man was lonely and it was "not good."  God created everything and called it good, but loneliness he called bad.

The creation of the woman from a part of the man (the “rib”) shows a unique relationship between the two. Marriage completes the man and woman in a metaphysical sense. The two become one flesh.

Once the woman was completed, in Genesis 2:22, it says God brought the woman to the man, like a father walks his daughter down the aisle.  This became a sort of wedding service where Eve's Father gave his daughter to another man.

God called her a "suitable helper," not a baby-maker, house cleaner or submissive slave.  God saw her as a partner for Adam—a part of him, making him complete. Just as the rib came from his side, the woman and man would go through life side-by-side, working together as equal partners with different roles and responsibilities.

The whole idea of marriage came from the original creation story, as God created woman from man, then instituted a relationship where they completed themselves through a new union.