Romans 4:1

The apostle proceeds to prove his main conclusion, Romans 3:28, which is, that a sinner is justified by faith without works, from the example of Abraham. He was a man that had faith and works both, yet he was justified by faith, and not by works; and who doubts but the children are justified after the same manner that their father was: there is but one way of justification; this is the connexion.

As pertaining to the flesh: these words may either be referred to father; and then they import no more but that Abraham was their father according to the flesh, Romans 9:5. Or else they may be referred to the following word found; and then the question is, What hath Abraham found, i.e. got or attained, according to the flesh? The sense is, What hath he got by his righteousness, which stands in works, and are done in the flesh? Abraham obtained not righteousness by any works, ceremonial or moral. So the word flesh is taken, {see Philippians 3:3,Philippians 3:4} when under the word flesh came circumcision, our own righteousness, which is by the law, or whatsoever is or may be opposed to that righteousness which is by the faith of Christ.