'Therefore it is of faith, that it might be by grace; to the end the promise might be sure to all the seed; not to that only which is of the law, but to that also which is of the faith of Abraham; who is the father of us all.' Romans 4: 16
The promise is sure. The guarantee is grace! The provision is faith! In today's world, we operate on the principle of warranty and guarantee all the time. You may purchase for example, as my wife did yesterday, an electric knife from Black and Decker with a two-year limited warranty. There are not many things with a lifetime guarantee; but this coming verse is the guarantee to all the descendants not only to those who are of the Law, but also to those who are of the faith of Abraham.
The next 5 verses outline how Abraham got the guarantee and how we can as well. They are the provisions of the guarantee. You have to believe that God:
1) 'calleth those things which be not, as though they were.' God gives life to that which is dead and calls into being what does not yet exist. Romans 4:17
2) 'against hope believed in hope.' Romans 4:18
3) 'And being not weak in faith, he considered not his own body.' Romans 4:19 When you consider yourself or situation do not waver in unbelief at God's promise.
4) 'He staggered not at the promise ofGod through unbelief; but was strong in faith, giving glory to God.' Romans 4:20 It means to not doubt, hesitate, or stagger at the promise of God, but be strong giving glory to God.
5) 'And being fully persuaded that what he had promised, he was able also to perform.' Romans 4: 21 Being absolutely convinced, fully assured, and certain that what he has promised, he is able to do, or to make good.
When Abraham was a hundred years old, he considered not his own body now dead, neither yet the deadness of Sara's womb and wavered not at the promise of God, namely the promise of God recorded in Genesis 15:5 that he should have a seed. That seed mentioned in Genesis 12:3 through whom all nations should be blessed is Jesus Christ. Faith was reckoned to Abraham for righteousness. Likewise, our faith can be reckoned to us for righteousness.