Under what circumstances was it credited? Was it after he was circumcised, or before? It was not after, but before!
And he received the sign of circumcision, a seal of the righteousness that he had by faith while he was still uncircumcised.1 So then, he is the father2 of all who believe3 but have not been circumcised, in order that righteousness might be credited to them.
References for Romans 4:11
And he is also the father of the circumcised who not only are circumcised but who also walk in the footsteps of the faith that our father Abraham had before he was circumcised.
It was not through law that Abraham and his offspring received the promise4 that he would be heir of the world,5 but through the righteousness that comes by faith.6
References for Romans 4:13
For if those who live by law are heirs, faith has no value and the promise is worthless,7
References for Romans 4:14
because law brings wrath.8 And where there is no law there is no transgression.9
References for Romans 4:15
Therefore, the promise comes by faith, so that it may be by grace10 and may be guaranteed11 to all Abraham's offspring--not only to those who are of the law but also to those who are of the faith of Abraham. He is the father of us all.12
References for Romans 4:16
As it is written: "I have made you a father of many nations."13 He is our father in the sight of God, in whom he believed--the God who gives life14 to the dead and calls15 things that are not16 as though they were.
References for Romans 4:17
Against all hope, Abraham in hope believed and so became the father of many nations,17 just as it had been said to him, "So shall your offspring be."18
References for Romans 4:18
Without weakening in his faith, he faced the fact that his body was as good as dead19--since he was about a hundred years old20--and that Sarah's womb was also dead.21
References for Romans 4:19
Yet he did not waver through unbelief regarding the promise of God, but was strengthened22 in his faith and gave glory to God,23
References for Romans 4:20