Jamieson, Fausset & Brown

Abraham . . . justified by works--evidentially, and before men (see on Jam 2:18). In Jam 2:23, James, like Paul, recognizes the Scripture truth, that it was his faith that was counted to Abraham for righteousness in his justification before God. when he had offered--rather, "when he offered" [ALFORD], that is, brought as an offering at the altar; not implying that he actually offered him.