Piper briefly discusses 1 Corinthians 7:9 in the sermon "Marriage, Singleness, and the Christian Virtue of Hospitality":
I should say just one brief word about that infamous sentence in 1 Corinthians 7:9: “If they cannot exercise self-control, they should marry. For it is better to marry than to burn with passion.” Remember, this is addressed explicitly to men and women (v. 8). And here is the one thing I want to say about it: When a person seeks to be married, knowing that as a single he or she would “burn with passion,” it doesn’t have to mean that marriage becomes a mere channel for the sex drive. Paul would never mean that in view of Ephesians 5.
Instead when a person marries—let me simply use the man as an example—he takes his sexual desire, and he does the same thing with it that we must all do with all our physical desires if we would make them means of worship—1) he brings it into conformity to God’s word; 2) he subordinates it to a higher pattern of love and care; 3) he transposes the music of physical pleasure into the music of spiritual worship, 4) he listens for the echoes of God’s goodness in every nerve; 5) he seeks to double his pleasure by making her joy his joy; and 6) he gives thanks to God from the bottom of his heart because he knows and he feels that he never deserved one minute of this pleasure.