Romans 4:19

It is He Himself, therefore, that makes those men good, to do good works. For He did not promise them to Abraham because He foreknew that of themselves they would be good. For if this were the case, what He promised was not His, but theirs. But it was not thus that Abraham believed, but “he was not weak in faith, giving glory to God;” and “most fully believing that what He has promised He is able also to perform.” He does not say, “What He foreknew, He is able to promise;” nor “What He foretold, He is able to manifest;” nor “What He promised, He is able to foreknow:” but “What He promised, He is able also to do.” It is He, therefore, who makes them to persevere in good, who makes them good. But they who fall and perish have never been in the number of the predestinated. …

Ver. 19 . “And being not weak in faith, he considered his own body now dead.” 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.

“If thou confess with thy mouth the Lord Jesus, and believe in thy heart that God hath raised Him from the dead, thou shalt be saved.” Then again that we may not seem to be making it contemptible by showing it to be easy and cheap, observe how he expands his account of it. For he does not come immediately to the words just given, but what does he say? “But the righteousness which is of faith saith on this wise; Say not in thine heart, Who shall go up into heaven? (that is, to bring Christ down); or, Who shall descend into the deep? (that is, to bring up Christ again from the dead.”) For as to the virtue manifested in works there is opposed a listlessness, which relaxeth our labors, and it requireth a very wakeful soul not to yield to it: thus, when one is required to believe, there are reasonings which confuse and make havoc of the minds of most men, and it wants a soul of some vigor to …

5. There is much to tell of faith, and the whole day would not be time sufficient for us to describe it fully. At present let us be content with Abraham only, as one of the examples from the Old Testament, seeing that we have been made his sons through faith. He was justified not only by works, but also by faith: for though he did many things well, yet he was never called the friend of God, except when he believed. Moreover, his every work was performed in faith. Through faith he left his parents; left country, and place, and home through faith. In like manner, therefore, as he was justified be thou justified also. In his body he was already dead in regard to offspring, and Sarah his wife was now old, and there was no hope left of having children. …