From The Bondage of the Will by Martin Luther (1483-1546):
In John 6:44, Christ says, "No man can come to me, except the Father which has sent me draw him." This leaves absolutely no room for "free will." The Lord goes on to explain the Father’s drawing, "Every man therefore that has heard, and has learned of the Father, comes to me" (verse 45). Man’s will, left to itself, is powerless to do anything about coming to Christ for salvation. Even the very word of the Gospel is heard in vain, unless the Father Himself speaks to the heart and draws us to Christ.