NET

20 He did not waver in unbelief about the promise of God but was strengthened in faith, giving glory to God.

Darby

20 and hesitated not at the promise of God through unbelief; but found strength in faith^D8024, giving glory to God;

Darby Bible Notes

faith - 'Found strength in faith' may be rather free, but 'strengthened by faith' might very easily be applied to his body, whereas it means that he was inwardly strengthened by faith. It is, I apprehend, in opposition to 'hesitating through unbelief.' Literally, it is 'gifted with strength.' Abraham was gifted with strength by faith (i.e. inwardly, in contrast with doubt).

KJV

20 He staggered not at the promise of God through unbelief; but was strong in faith, giving glory to God;