"Perhaps a fear of neighboring peoples encouraged the Jews to focus on the priority of re-establishing their relationship with God. Restoring worship of God might ward off danger, because God's presence would protect the people." (The Preacher's Commentary) God responds actively to altar activity. He is drawn to the altar. He is attracted to the altar. He is moved by the altar. It is a "magnet" for His presence and glory. Hence, He is saying to His people - "Build Me an altar."