Rom 4:5 But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness.
To believe on, is not just believing something.
Jas 2:17 Even so faith, if it hath not works, is dead, being alone.
Jas 2:18 Yea, a man may say, Thou hast faith, and I have works: shew me thy faith without thy works, and I will shew thee my faith by my works.
Jas 2:19 Thou believest that there is one God; thou doest well: the devils also believe, and tremble.
Jas 2:20 But wilt thou know, O vain man, that faith without works is dead?
Jas 2:21 Was not Abraham our father justified by works, when he had offered Isaac his son upon the altar?
Jas 2:22 Seest thou how faith wrought with his works, and by works was faith made perfect?
LA
James was writing to the scattered sheep of the House of Israel, not
to the Gentiles. (Us)