Rom 4:20

“For God neither gave any proof nor made any sign, but there were only bare words promising such things as nature did not hold out any hopes of. Yet still he says, "he staggered not." He does not say, "He did not disbelieve," but, "He staggered not," that is, he neither doubted nor hesitated though the hindrances were so great. From this we learn, that if God promise even countless impossibilities, and he that heareth doth not receive them, it is not the nature of things that is to blame, but the unreasonableness of him who receiveth them not. "But was strong in faith." See the pertinacity of Paul. For since this discourse was about them that work and them that believe, he shows that the believer works more than the other, and requires more power, and great strength, and sustains no common degree of labor. For they counted faith worthless, as having no labor in it. Insisting then upon this, he shows that it is not only he that succeeds in temperance, or any other virtue of this sort, but he that displays faith also who requires even greater power. For as the one needs strength to beat off the reasonings of intemperance, so hath the faithful also need of a soul endued with power, that he may thrust aside the suggestions of unbelief. How then did he become "strong?" By trusting the matter, he replies, to faith and not to reasonings: else he had fallen. But how came he to thrive in faith itself? By giving glory to God, he says.”

“Note how he proves that the believer has need of great strength. Many disparaged faith as a matter requiring no labor, while they exalted works as requiring sweat and strength. But the apostle says that the believer has need of a great and mighty soul, so as to repel the suggestions of unbelief, just as Abraham was strong in faith. And how was Abraham strong in faith? "Giving glory to God," that is, not believing through human reasoning, but thinking within himself thoughts worthy of the glory of God, and being fully persuaded that God is able to do the impossible; for in this consists the glory of God.”

“Then when he says, in the promise also of God, he commends Abraham's faith in the repeated promise that his seed would be exalted. First, he mentions the firmness of faith; second, the cause of the firmness, at giving glory to God. First, therefore, he says: in the promise also of God, i.e., the promise that his seed would be exalted or that it would be multiplied, which was repeated: look toward heaven and number the stars. . . . So shall your descendants be (Gen 15:5); you shall be the father of a multitude of nations (Gen 17:4); I will multiply your descendants as the stars of heaven (Gen 22:17). Or, in the promise of God can refer to the exaltation of his descendants, because when he had said: I will multiply your descendants, he added at once: and your descendants shall possess the gates of their enemies and by your descendants shall all the nations of the earth be blessed. Concerning this promise of God he staggered not by distrust, i.e., he did not doubt the truth of the divine promise: he who doubts is like a wave of the sea that is driven and tossed by the wind (Jas 1:6); but was strengthened in faith, i.e., clung firmly to his belief: resist him, firm in your faith (1 Pet 5:9).”