Romans 4:11

4:11 And he received the sign of circumcision as a seal of the righteousness that he had by faith while he was still uncircumcised, so that he would become the father of all those who believe but have never been circumcised, that they too could have righteousness credited to them.

Romans 4:19-20

4:19 Without being weak in faith, he considered his own body as dead (because he was about one hundred years old) and the deadness of Sarah’s womb. 4:20 He did not waver in unbelief about the promise of God but was strengthened in faith, giving glory to God.