Jamieson, Fausset and Brown on James 2:24

24. justified and, not by faith only--that is, by "faith without (separated from: severed from) works," its proper fruits (see on Jas 2:20). Faith to justify must, from the first, include obedience in germ (to be developed subsequently), though the former alone is the ground of justification. The scion must be grafted on the stock that it may live; it must bring forth fruit to prove that it does live.