The Gospel is the Good News that Jesus Christ, who is the Son of God and God Incarnate, out of unmatched grace and love for all humanity, died on the cross for the forgiveness of all the sins of all people (mine!) and that He rose again from death to life on the third day.
Those who simply believe in this Gospel (found in 1st Corinthians 15:1-4), even for a moment, are forever saved (John 3:16 and John 6:47), regardless of any sins or good works they do or do not do after that point.
They are instantaneously forgiven of all of their sins, they are saved from the just punishment for their sins in Hell, they are saved from eternal separation from God, they have irrevocable eternal life as a present possession, they have a new holy identity in Christ, they have God as their Father, they are indwelled by the Holy Spirit, and they will go to Heaven immediately when they die.
By believing in Jesus as Savior, they have thereby repented of their unbelief; and they have been spiritually baptized by the Spirit into the death and resurrection of Christ (1st Corinthians 12:13).
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Second, when a believer in Christ, (who is already irrevocably saved and sanctified without any good works of his or her own), lives by faith in Christ in him, as a child of God, that he has died with Christ on the cross and been risen with Christ to new, perfect, holy and eternal life, by His grace and love and Spirit, this is known as practical sanctification.
By this we can become Christlike.
If we live by faith and love and obedience to His Spirit, (though we are never without the ability to sin, because of the sinful flesh and free will), we will become practically sanctified, and we will live in loving communion with God even in this present life on earth.
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Jesus is our salvation; and Jesus is also our sanctification. –C.S.
Grace, Insight, and Art 