I will greatly rejoice in the LORD, my soul shall be joyful in my God; for He hath clothed me with the garments of salvation, He hath covered me with the robe of righteousness, as a bridegroom decketh himself with ornaments, and as a bride adorneth herself with her jewels. – Isaiah 61:10

Our union to Christ is practically and experimentally wrought in us by faith when a man giveth himself up to Christ, to sink or swim with Christ, when he leaneth his soul wholly on the Beloved, when as for his good works he abhorreth them, and as for his self-righteousness, he counteth it dross and dung, when he clingeth to the sole hope of the cross, then is such a man in Christ. He is further in Christ when he loves Jesus, when the heart having trusted and reposed in the cross, is moved with deep and warm affection to the Crucified, so that the soul clings to Christ, embracing Him with fervent love, and Christ becomes the Bridegroom, and the heart becomes His spouse, and they are married to one another in a union which no divorce can ever separate. When love and faith come together, then is there a blessedly sweet communion; these two graces become the double channel through which the Holy Spirit’s influence flows forth daily, making the Christian to grow up more fully unto Christ Jesus in all things. The riper the Christian becomes, the nearer to the glory, the closer to the perfection which is promised, the more completely will he think and act, and live and move, in Christ his Master, being one with Jesus in all things. I shall not detain you longer over that one matter, every true Christian is in Christ.~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/0881.cfm