This phrase is interesting because in it Paul brings together two opposing ideas: work and faith, which are often presented in an antithetical relationship in many of Paul’s epistles: “we hold that one is justified by faith apart from works of the law” (Rom. 3:28); “we know that a person is not justified by works of the law but through faith in Jesus Christ” (Gal. 2:16; 3:2). We can see why the two are set against each other. We already said that faith is an act of depending on God and His grace. Works, on the other hand, are “meritorious” deeds, which rightly deserve some kind of rewards. When Paul says that we cannot be justified by the works of the law, he is not saying that God refuses to acknowledge our merits; he is saying that we don’t have any legitimate works that are worthy of God’s reward: “we are all as an unclean thing, and all our righteousnesses are as filthy rags…” (Isa. 64:6).
But in other passages, works are used in a more generic sense: simply as something we do, which requires our conscious exertion of energy and effort. We see “works” used in this sense a lot in the Book of James: “What good is it, my brothers, if someone says he has faith but does not have works? Can that faith save him?” (Jam. 2:14); “as the body apart from the spirit is dead, so also faith apart from works is dead” (Jam. 2:26). As you can see, in these verses, faith and works are not pitted against each other: James takes pains to show the inextricable connection between the two. But you also notice that the word, “works,” is used by itself in these verses without “[works] of the law.”