"God reveals himself as an all-sufficient God, as one that is able to go through with all his engagements [including your sanctification as a Christian]. If you will stagger [at this], you may do so. [But] This [much] is certain, you have no cause to to do so from hence, - there is not any promise that ever God entered into but he is able to perform it."
-John Owen, "The Steadfastness of the Promises, and the Sinfulness of Staggering". A sermon drawn from Romans 4:20. Preached February 28, 1649. The Works of John Owen, Volume VIII. The Banner of Truth Trust: Carlisle, PA. (1649) 2000. p.225.