O foolish Galatians, who hath bewitched you, that ye should not obey the truth, before whose eyes Jesus Christ hath been evidently set forth, crucified among you? This only would I learn of you, Received ye the Spirit by the works of the law, or by the hearing of faith? Are ye so foolish? Having begun in the Spirit, are ye now made perfect by the flesh? Have ye suffered so many things in vain? If it be yet in vain. He therefore that ministereth to you the Spirit, and worketh miracles among you, doeth he it by the works of the law, or by the hearing of faith? Even as Abraham believed God, and it was accounted to him for righteousness.
Galatians 3:1-6
False teachers, men who were adding to the gospel, teaching that keeping of the law was a necessity for salvation. Paul is adamant with them concerning the truth of by grace through faith alone in Christ alone.
The Gospel of Jesus Christ is polluted every time there is an addition to the word of the gospel. The addition of Jewish Law such as circumcision, keeping the annual Feast days such as the Passover and the Day of Atonement (Yom Kippur), and the rest. If we add baptism as a necessity for salvation, then the gospel is tainted with the stench of dead flesh. The believing thief on the cross might have something to say about that.
Do not add to or diminish anything of the gospel of Jesus Christ. He came into the word to save lost sinners of whom I am the worst. Yet He loved me and saved me from my sins, from death, and from Hell. I believe Him. How about you?