The most foundational thing we can say about marriage is that it is God's doing. John Piper explains, "A glimpse into the magnificence of marriage comes from seeing in God's word that God himself is the great doer. Marriage is his doing. It is from him and through him."
In his book This Momentary Marriage, Pastor John gives four reasons why marriage is God's doing:
First, marriage was God's design.
While Genesis 1:27–28 makes clear that marriage is meant for male and female, the logic of Genesis 2 also confirms it.
In [Genesis 2:18], it is God himself who decrees that man's solitude is not good, and it is God himself who sets out to complete one of the central designs of creation, namely, man and woman in marriage. "It is not good that the man should be alone; I will make him a helper fit for him." Don't miss that central and all-important statement: God himself will make a being perfectly suited for him -- a wife.
[Read the rest of the article at Desiring God.]