Charles Ellicott Commentary Romans 4:20

"yet, looking unto the promise of God, he wavered not through unbelief, but waxed strong through faith, giving glory to God," — Romans 4:20 (ASV)

In faith.—Better, through or by faith, corresponding to through unbelief in the preceding clause. Unbelief did not make him doubt, but faith made him confident and strong.

Giving glory to God.—This phrase does not necessarily refer to a verbal ascription of praise, but may be used of anything which tends to God’s glory, whether in thought, word, or deed (Ezra 10:11; Jeremiah 13:16; Luke 17:18; John 9:24; Acts 12:23); here it seems to be applied to the frank recognition of God’s omnipotence involved in Abraham’s faith.