That the Holy Scriptures cannot be penetrated by study and talent is most certain. Therefore your first duty is to begin to pray, and to pray to this effect... that if it please God to accomplish something for His glory—not for yours or any other person's—He very graciously grant you a true understanding of His words. For no master of the divine words exists except the Author of these words, as He says: 'They shall be all taught of God' (John 6:45). You must, therefore, completely despair of your own industry and ability and rely solely on the inspiration of the Spirit.
--Martin Luther, 1518
(What Luther Says: An Anthology, Vol. 1, p. 77)
Quoted by John Piper: here