Moreover, we should refrain from debates about predestination and from similar discussions. They are fraught with danger and mischief, because they inquire into the will and hidden counsels of God apart from the Word. They want to investigate and explore too inquisitively why God has revealed Himself in one way or another, and why He so earnestly endeavors to persuade our will to believe. The inquisitiveness of Adam is well known. In Paradise he sought God apart from the Word, just as Satan did in heaven. Both found Him, but not without great harm.
Therefore let us learn that God must be apprehended, not with our reason but as He has revealed Himself and has condescended to speak and deal with us in human fashion. Indeed, we should joyfully welcome the Divine Majesty, who comes down to us with such humility that He not only invites us to Himself with promises but by inserting an oath even compels us to accept what the Word offers.
This same doctrine is set forth in an excellent manner in the Epistle to the Hebrews (6:16–18): “Men indeed swear by a greater than themselves, and in all their disputes an oath is final for confirmation. So when God desired to show more convincingly to the heirs of the promise the unchangeable character of His purpose, He interposed with an oath, so that through two unchangeable things, in which it is impossible that God should prove false, we who have fled for refuge might have strong encouragement to seize the hope set before us.”
Luther’s works, vol. 4: Lectures on Genesis: Chapters 21-25 p 143-144