Are you saying that the only thing that counts as works are the things in Mosaic law?
Man-made or not.
If the Law of God could not save, and it couldn't, then nothing that man substitutes for it can either.
Ephesians 2:4-7 But God, being rich in mercy, because of His great love with which He loved us, even when we were dead in our transgressions, made us alive together with Christ (by grace you have been saved), and raised us up with Him, and seated us with Him in the heavenly places in Christ Jesus, so that in the ages to come He might show the surpassing riches of His grace in kindness toward us in Christ Jesus.
Ephesians 2:8-9 For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast.