Didn't anyone quote Hebrews 11 about Faith to this guy?
Our belief on Jesus Christ is NOT a work. Like Apostle Paul taught,
Rom 4:4-5
4 Now to him that worketh is the reward not reckoned of grace, but of debt.
5 But to him that worketh not, but believeth on Him That justifieth the ungodly, his faith is counted for righteousness.
KJV
The logic is simple too. If someone says they will give us their old car not asking anything in return, and we believe that person, that is a show of faith, because we believe that person will do it, and we didn't have to do anything to earn that car through a debt owed.
That is exactly what happened with Abraham (minus the car object of course), when God gave Abraham the Promise (Gospel) by Faith, and Abraham believed God. Abraham didn't do anything for it, he simply believed God would fulfill what He said, and thus God counted Abraham's Faith as righteousness. Apostle Paul says that those of Faith thus have become the "children of Abraham" because of that (Galatians 3).