Christians know that Christians are those who believe in one God in three persons, who are saved through their faith in Jesus Christ, and His blood atonement for them on the cross, and nothing more. Because of Him, and their faith in Him, they are baptized and do good works, which are as filthy rags, save His infinite grace.
The filty rags terminology doesn’t come from me, it comes from the Bible:
“But we are all like an unclean thing, and all of our righteousnesses are like filthy rags” (Isa. 64:6).
This verse is to remind us that, compared to God’s glorious perfection, we fall short of the glory of God. It is a warning about being vain about our “good works”, that they cannot save us or make us in any way worthy.
Only the perfect Sacrifice, Jesus Christ, can do that.
The Biblical truths I’ve told you are not “the filthy work of mud throwing.” They are necessary to put into perspective our dependence on Jesus for everything, even the good works we do. And the New Testament teaches that we don’t do our good works to GET saved, we do them because we ARE saved.