Romans 4:3-6

4:3 For what does the scripture say? “Abraham believed God, and it was credited to him as righteousness.” 4:4 Now to the one who works, his pay is not credited due to grace but due to obligation. 4:5 But to the one who does not work, but believes in the one who declares the ungodly righteous, his faith is credited as righteousness.

4:6 So even David himself speaks regarding the blessedness of the man to whom God credits righteousness apart from works:

Romans 4:9-10

4:9 Is this blessedness then for the circumcision or also for the uncircumcision? For we say, “faith was credited to Abraham as righteousness.” 4:10 How then was it credited to him? Was he circumcised at the time, or not? No, he was not circumcised but uncircumcised!

Romans 4:21-22

4:21 He was fully convinced that what God promised he was also able to do. 4:22 So indeed it was credited to Abraham as righteousness.