Christ is all, and in all. – Colossians 3:11

There are some who think that Christ is all in some things, but they have not yet seen the full teaching of the text; for it saith: “Christ is all, and in all.” He is all, “say they, in justification; He it is that pardons all our sins and covers us with His righteousness, but as to our sanctification, surely, we are to effect that ourselves; and as to our final perseverance, it must depend wholly upon our own watchfulness. Are we not in jeopardy still? Are there not some points which depend upon our own virtue and goodness?” Beloved, God forbid I should say a word against the most earnest watchfulness, against the most diligent endeavors, but I beseech you do not place them in a wrong position or speak as though the ultimate salvation of the believer were based upon such shifting sand. 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. ~ C.H. Spurgeon

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