God has been wont to pass His servants through some special discipline if His intention has been to use them for any particular service. He shapes and prepares the vessels that He deigns to make use of, and often by means of severe trials, in order to fit them for their work.
David was a man after God's own heart, but he had to endure years of affliction even after being anointed king. He was hunted like a partridge on the mountains. Never, however, let us forget that but for these circumstances we should have been without most of his psalms, and that his sufferings from within and without, his exercises of soul, and the persecution of his enemies were the occasions which called them forth. So it was in Paul's case. But for his Roman prison, we might not have had many of his valuable epistles. Thus does God bring the greatest blessing out of the keenest suffering and the deepest affliction of His children.