Isaac was the child of promise. "In Isaac shall thy seed be called." With reiterated emphasis this lad had been indicated as the one essential link between the aged pair and the vast posterity which was promised them. And now the father was asked to sacrifice his life. It was a tremendous test to his faith. How could God keep His word, and let Isaac die? It was utterly inexplicable to human thought. If Isaac had been old enough to have a son who could perpetuate the seed to future generations, the difficulty would have been removed. But how could the childless Isaac die; and still the promise stand of a posterity through him, innumerable as stars and sand? One thought, however, as the Epistle to the Hebrews tells us, filled the old man's mind, "GOD IS ABLE." He "accounted that God was able to raise him up, even from the dead" (Hebrews 11:19). He felt sure that somehow God would keep His word. It was not for him to reason how, but simply to obey. He had already seen Divine power giving life where all was as good as dead; why should it not do it again? In any case he must go straight on, doing as he was told, and calculating on the unexhausted stores in the secret hand of God. Oh for faith like this! -- simply to believe what God says; assured that God will do just what He has promised; looking without alarm, from circumstances that threaten to make the fulfillment impossible, to the bare word of God's unswerving truthfulness. Surely this habit is not so impossible of attainment. Why then should we not begin to practice it, stepping from stone to stone, until we are far out from the shore of human expediency leaning on the unseen but felt arm of Omnipotence?