What shall we say then? - See Romans 3:1. This is rather the objection of a Jew. “How does your doctrine of justification by faith agree with what the Scriptures say of Abraham? Was the Law set aside in his case? Did he derive no advantage in justification from the rite of circumcision, and from the covenant which God made with him?” The object of the apostle now is to answer this inquiry.
That Abraham our father - Our ancestor; the father and founder of the nation; see the note at Matthew 3:9 The Jews valued themselves much on the fact that he was their father; and an argument, drawn from his example or conduct, therefore, would be especially forcible.
As pertaining to the flesh - This expression is one that has been much controverted. In the original, it may refer either to Abraham as their father “according to the flesh,” that is, their natural father, or from whom they were descended; or it may be connected with “hath found.” “What shall we say that Abraham our father hath found in respect to the flesh?” κατὰ σάρκα kata sarka. The latter is doubtless the proper connection. Some refer the word “flesh” to external privileges and advantages; others to his own strength or power (Calvin and Grotius); and others make it refer to circumcision. This latter I take to be the correct interpretation. It agrees best with the connection, and equally well with the usual meaning of the word. The idea is, “If people are justified by faith; if works are to have no place; if, therefore, all rites and ceremonies, all legal observances, are useless in justification; what is the advantage of circumcision? What benefit did Abraham derive from it? Why was it appointed? And why is such an importance attached to it in the history of his life.” A similar question was asked in Romans 3:1.
Hath found - Hath obtained. What advantage has he derived from it?