For God expresses His promises in such a manner that when He promises grace and blessing He remains God. If His promise should be and remain firm, it is also necessary for God to remain and be acknowledged as the One who bestows and promises. But if I am proud, then I lose the promise; for the promise excludes pride and includes humility and the knowledge of God, who gives the promise.
Luther’s works, vol. 5: Lectures on Genesis: Chapters 26-30 p 94-95