If Salvation were by works, then only the Jews would be saved because they were under the covenant of the law (works) who got circumcised and were supposed to obey the ten commandments.
But the fact that Gentiles (uncircumcised) are allowed to be saved proves that salvation is by Grace through Faith and not works!
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.”
Acts 15 “7 After much discussion, Peter got up and addressed them: “Brothers, you know that some time ago God made a choice among you that the Gentiles might hear from my lips the message of the gospel and believe. 8 God, who knows the heart, showed that he accepted them by giving the Holy Spirit to them, just as he did to us. 9 He did not discriminate between us (Jews) and them (Gentiles), for he purified their hearts by faith. 10 Now then, why do you try to test God by putting on the necks of Gentiles a yoke that neither we nor our ancestors have been able to bear? 11 No! We believe it is through the GRACE of our Lord Jesus that we (Jews) are saved, just as they (Gentiles) are.””
Ephesians 2 “11 Therefore, remember that formerly you who are Gentiles by birth and called “uncircumcised” by those who call themselves “the circumcision” (which is done in the body by human hands)— 12 remember that at that time you were separate from Christ, excluded from citizenship in Israel and foreigners to the covenants of the promise, without hope and without God in the world. 13 But now in Christ Jesus you who once were far away have been brought near by the blood of Christ. 14 For he himself is our peace, who has made the two groups one and has destroyed the barrier, the dividing wall of hostility, 15 by setting aside in his flesh the law with its commands and regulations. His purpose was to create in himself one new humanity out of the two, thus making peace, 16 and in one body to reconcile both of them to God through the cross, by which he put to death their hostility. 17 He came and preached peace to you who were far away and peace to those who were near. 18 For through him we both have access to the Father by one Spirit.”
On the Cross, the Law of works came to an end.
The Law and its’ commandments ended.
This is why Salvation is now by Grace through Faith and not works!
Romans 3 “21 But now apart from the law the righteousness of God has been made known, to which the Law and the Prophets testify. 22 This righteousness is given through faith in Jesus Christ to all who believe. There is no difference between Jew and Gentile, 23 for all have sinned and fall short of the glory of God, 24 and all are justified freely by his grace through the redemption that came by Christ Jesus. 25 God presented Christ as a sacrifice of atonement, through the shedding of his blood—to be received by faith.”