For we are members of His body, of His flesh, and of His bones- Ephesians 5:30

“We”, that is His believing people, “are members of His body, and of His flesh, and of His bones.” He is our Head, and we are the members of the body, and so we are joined to Him by a living, loving, lasting union.

Now what does this living union to Christ mean? It means Christ’s life laying hold of us. “For as the Father hath life in Himself; so hath He given to the Son to have life in Himself.” He is full of life, and when He takes hold of us, and raises our life into His, there is truly a living union between Him and us.

The union of a soul to Christ is made so sweet because it is as loving as it is living! Christ’s love to us begins this loving union. Its source is not in ourselves; but in love eternal, love immeasurable, love which caused itself, free-grace love, love to the unworthy, love to enemies, love to those who had no life, no strength, and no hope apart from Him. Christ loved us so that He deigned to join Himself to us in eternal union. The great Artesian well from which we drink, and which has tapped the divine fountains, is the love of Christ.

O friends, what a sad thing it would be for anyone to have only a temporary union with Christ! Why, you are not building at all unless your building stands; and you are not truly in union with Christ unless the union is lasting union; and it will not be unless it is a living union! Be satisfied with nothing short of that union which the Spirit of God works in the hearts of those who, without reserve, yield to His power.~ C.H. Spurgeon

https://www.blueletterbible.org/Comm/spurgeon_charles/sermons/2245.cfm