People like to use that but it's not true. Paul distinctly uses "works of the law" when he means "works of the law". In Romans 11:6 does not use "works of the law". Also in Ephesians he again uses works so no one could boast.
Ephesians 2:8 For it is by grace you have been saved, through faith--and this is not from yourselves, it is the gift of God-- 9 not by works, so that no one can boast.
He is clearly stating that what man does is not how he gets saved. It's "by grace through faith". He said "not from yourselves. In other words not something you do.
That's true... to a point. From there, you have to remember that we are sinners constantly being saved. It is not once saved, always saved. It's more like... now that you're saved, stay saved. The Corporal Works of Mercy are not works to earn our salvation like coins of the realm. They are chastisements of the flesh to orient us toward God's Will. They are self-denial and sacrifice in the service of Love. It isn't that we buy our way into Heaven, it is more of a walk along the path to our journey's end.