Romans 4:20 Meaning

18Who against hope believed in hope, that he might become the father of many nations, according to that which was spoken, So shall thy seed be.

19And being not weak in faith, he considered not his own body now dead, when he was about an hundred years old, neither yet the deadness of Sara's womb:

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

21And being fully persuaded that, what he had promised, he was able also to perform.

22And therefore it was imputed to him for righteousness.