But of Him you are in Christ Jesus, who became for us wisdom from God—and righteousness and sanctification and redemption— – 1 Corinthians 1:30

We are saved in Christ. We are complete in Him. We are sanctified in Christ Jesus: “And He is made of God unto us wisdom, righteousness, sanctification, and redemption.” Christ is all, not in my justification only, but in my sanctification too. He is all, not only in the first steps of my faith, but in the last. “He is Alpha and Omega; He is the beginning and the ending, saith the Lord.” There is no point between the gates of hell and the gates of heaven where a believer shall have to say, “Christ fails me here, and I must rely upon my own endeavors. From the dunghill of our corruption up to the throne of our perfection there is no point left to hazard, or set aside for us to supply; our salvation has Christ to begin with, Christ to go on with, and Christ to finish with, and that in all points, at all times, for every man of woman born that ever shall be saved. There is no point in which the creature comes in to claim merit, or to bring strength, or to make up for that which was lacking. “Christ is all, and in all.” The saints are “perfect in Christ Jesus.” He said, “it is finished,” and finished it is. He is not the author of our faith only, but the finisher of it too. He is all in all, and man is nothing at all.

This is a truth which every believer has recognised. There are a great many differences among believers, but there is no difference as to this essential point. ~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/1006.cfm