Years ago I read most of John Murray's little book
Redemption: Accomplished and Applied (Eerdmans, 1955)--most, but not all. It is a great book that I have often gone back to in teaching in order to refresh myself with aspects of salvation. In one of those weird twists of life I had never finished the book and so I never read chapter 9 entitled "Union with Christ"--that is, until last week. WOW! Murray is not known for flowery prose but his unpacking of this truth was simply awesome. Here are few lines that moved me:
Nothing is more central or basic than union and communion with Christ. (p. 161)
Apart from union with Christ we cannot view past, present, or future with anything but dismay and Christless dread. By union with Christ the whole complexion of time and eternity is changed and the people of God may rejoice with joy unspeakable and full of glory. (p. 165)
The life of faith is the life of love, and the life of love is the life of fellowship, or mystic communion with him who ever lives to make intercession for his people and who can be touched with the feeling of our infirmities. It is fellowship with him who has an inexhaustible reservoir of sympathy with his people's temptations, afflictions, and infirmities because he was tempted in all points like as they are, yet without sin. The life of true faith cannot be that of cold metallic assent. It must have the passion and warmth of love and communion because communion with God is the crown and apex of true religion. "Truly our fellowship is with the Father and with his Son Jesus Christ (1 John 1:3).
Union with Christ is the central truth of the whole doctrine of salvation. (p. 170)
There is no truth, therefore, more suited to impart confidence and strength, comfort and joy in the Lord than this one of union with Christ. (p. 171).