John Chrysostom

Do you see how he gives the obstacles, as well as the high spirit of the righteous man which surmounts all? "Against hope," he says, was that which was promised: this is the first obstacle. For Abraham had no other person who had received a son in this way to look to. They that were after him looked to him, but he to no one, save to God only. And this is why he said, "against hope." Then, "his body now dead." This is a second. And, "the deadness of Sarah's womb." This is a third, aye and a fourth obstacle.