Actually, no. He wasn't, and it was indeed about justification, not sanctification. I'm not sure how you got that so backward, so here is what James actually said...in brief:
James 2:14, 17, 20-22, 24
14 What doth it profit, my brethren, though a man say he hath faith, and have not works? can faith save him? ...
17 Even so faith, if it hath not works, is dead, being alone. ...
20 But wilt thou know, O vain man, that faith without works is dead?
21 Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar?
22 Seest thou how faith wrought with his works, and by works was faith made perfect? ...
24 Ye see then how that by works a man is justified, and not by faith only.
Sanctification isn't even mentioned in the entirety of the book of James that I can find using Blue Letter Bible online.
Perhaps you didn't mean to say it that way, and therefore have a clarification?
MM