Romans 4:4 - Matthew Poole's English Annotations on the Holy Bible

He proceeds to prove, that Abraham was not justified by works, but by faith, and free grace, and so had no cause of boasting. This he illustrates by a comparison betwixt one that worketh, and one that worketh not, but believeth. To him that worketh; i.e. to him that worketh with a design or intent to obtain or merit justification by his works, for else he that believeth also worketh; only he is said not to work, secundum quid, after a sort, to the end or intent that he might merit by it. Is the reward not reckoned of grace, but of debt; he speaks this by way of supposition, in case he should have fulfilled the condition of perfect obedience: and yet, to speak properly, there is no reward, as a due debt from God to him that worketh, Romans 11:35; only he speaks after the manner of men, and useth a civil maxim, taken from human affairs.