Romans 4:4-5

⁴ Now to him who works, the wages are not counted as grace but as debt.

⁵ But to him who does not work but believes on Him who justifies the ungodly, his faith is accounted for righteousness,

works = fulfilling the requirements of the law

debt — if justification is owed due to works, it isn’t by grace

Works are forbidden as a means to justification.