The fundamental reason that the Word of God is essential to joy in God is that God reveals himself mainly by his word. And seeing this revelation of God is the foundation of our joy. As it was in the days of Samuel, so it is today (I Samuel 3:21). When it says, “The LORD appeared,” it says something amazing. God was seen not with the eyes of the head, but with the eyes of the heart, for God is “the king of ages, immortal, invisible, the only God” (I Timothy 1:17). And though it may seem strange, this seeing at Shiloh happened “by the word of the Lord.” As the Word was heard, the Lord was seen. In the hearing was the seeing. The spiritual hearing of God’s Word becomes the spiritual seeing of God’s glory.
– Piper, John; When I Don’t Desire God: How to Fight for Joy; Crossway; Wheaton, Ill.; copyright 2004; p. 95