Adam Clarke on James 2:18

Show me thy faith without thy works - Your pretending to have faith, while you have no works of charity or mercy, is utterly vain: for as faith, which is a principle in the mind, cannot be discerned but by the effects, that is, good works; he who has no good works has, presumptively, no faith.

I will show thee my faith by my works - My works of charity and mercy will show that I have faith; and that it is the living tree, whose root is love to God and man, and whose fruit is the good works here contended for.