The phrase “works of the law” (erga nomou) as it appears in Rom. 3.20, 27, 28; Gal. 2.16; 3.2, 5, 10 has been understood in different ways.
Jewish ceremonies.
Boundary markers between Jews and Gentiles.
The entire Jewish law.
Laws obeyed in a legalistic spirit.
Calvin’s Commentary on Romans on Rom 3:20 says this about works of the law: “It is a matter of doubt, even among the learned, what the works of the law mean. Some extend them to the observance of the whole law, while others confine them to the ceremonies alone. The addition of the word law induced Chrysostom, Origen, and Jerome to assent to the latter opinion.”
Many proponents of the New Perspective on Paul identified the works of the law as the laws that served to ensure Israel's separateness from Gentiles, i.e., circumcision, sabbath-keeping, and food laws.
But is that really the case?