John Chrysostom

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. …

Homily on Romans VIII ↗

Theophylact of Ohrid

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? …

Commentary on Romans ↗

Thomas Aquinas

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. . . . …

Commentary on Romans ↗