Salvation is by Grace

Acts 4:12 Neither is there salvation in any other: for there is none other name under heaven given among men, whereby we must be saved.

Jesus is the only way to salvation.

Ephesians 2:8-10 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
2:9 Not of works, lest any man should boast.
2:10 For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.

Salvation is wholly the work of God, and the gift of God, and cannot be found through our own works, but only by the grace of God through faith in Christ Jesus.

As new creatures in Christ, the regenerate person is enabled through the indwelling of the Holy Spirit to do good works.

Galatians 2:21 I do not frustrate the grace of God: for if righteousness come by the law, then Christ is dead in vain.

Galatians 3:21 Is the law then against the promises of God? God forbid: for if there had been a law given which could have given life, verily righteousness should have been by the law.

If we can be saved by our own works then Christ died for nothing. There was no law which could have been given, nor any work that we might do, that we may obtain salvation.

Galatians 5:1-4 Stand fast therefore in the liberty wherewith Christ hath made us free, and be not entangled again with the yoke of bondage.
5:2 Behold, I Paul say unto you, that if ye be circumcised, Christ shall profit you nothing.
5:3 For I testify again to every man that is circumcised, that he is a debtor to do the whole law.
5:4 Christ is become of no effect unto you, whosoever of you are justified by the law; ye are fallen from grace.

Paul is telling the Galatians that they are fallen from grace if they believe that they can be justified by the works of the Jewish law. He says that Christ shall profit you nothing; that means you cannot be saved unless you totally rely on the finished work of Jesus for salvation apart from your own works, whether they be the works of the Mosaic law or any other works, to believe that justification can be had by our works is to reject Christ as our only means of salvation.

It is in effect putting faith in yourself rather than God. Justification is given only by faith in the finished work of Jesus Christ, and to deny that salvation is by grace through faith apart from works is to reject salvation itself. This is an essential doctrine of Christianity.

Read also Romans 3-5, Romans 10:1-10, and Galatians 3-5

James 2:18 Yea, a man may say, Thou hast faith, and I have works: show me thy faith without thy works, and I will show thee my faith by my works.

1Jo 2:3-5 And hereby we do know that we know him, if we keep his commandments.
2:4 He that saith, I know him, and keepeth not his commandments, is a liar, and the truth is not in him.
2:5 But whoso keepeth his word, in him verily is the love of God perfected: hereby know we that we are in him.

Good works are, however, the mark of a truly regenerate person. The salvation of a person who continues in a sinful lifestyle is seriously in question, as good works and obedience to God are the visible manifestation of the indwelling Holy Spirit.