John Calvin Reformed @genevareformer

5. But believes on him, etc. This is a very important sentence, in which he expresses the substance and nature both of faith and of righteousness. He indeed clearly shews that faith brings us righteousness, not because it is a meritorious act, but because it obtains for us the favor of God.

Matthew Henry Presbyterian @wholebiblehenry

Here the apostle proves that Abraham was justified not by works, but by faith. Those that of all men contended most vigorously for a share in righteousness by the privileges they enjoyed, and the works they performed, were the Jews, and therefore he appeals to the case of Abraham their father, and puts his own name to the relation, being a Hebrew of the Hebrews: Abraham our father.

Commenting on Romans 4:1-8

John Gill Reformed Baptist @doctorgill

But to him that worketh not,.... Not that the believer does not work at all, but not from such principles, and with such views as the other; he does not work in order to obtain life and salvation; he does not seek for justification by his doings: but believeth on him that justifieth the ungodly: or that ungodly one: particular reference is had to Abraham...