Romans 4:21

And being fully persuaded that, what he had promised, he was able also to perform.

And being fully persuaded,.... He had not only faith, a strong faith, but full assurance of faith:

that what he God had promised; though it was so long ago, and there were so many difficulties in the way;

he was able, being the Lord God Almighty,

to perform; so his faith rested upon the power of God, with whom nothing is impossible.