“Union with Christ is the central truth of the whole doctrine of salvation. All to which the people of God have been predestined in the eternal election of God, all that has been secured and procured for them in the once-for-all accomplishment of redemption, all of which they become the actual partakers in the application of redemption, and all that by God’s grace they will become in the state of consummated bliss is embraced within the compass of union and communion with Christ…
It is out of the measureless fullness of grace and truth, of wisdom and power, of goodness and love, of righteousness and faithfulness which resides in Christ that God’s people draw for all their needs in this life and for the hope of the life to come. 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.
It also promotes sanctification, not only because all sanctifying grace is derived from Christ as the crucified and exalted Redeemer, but also because the recognition of fellowship with Christ and of the high privilege it entails incites to gratitude, obedience, and devotion. Union means also communion and communion constrains a humble, reverent, loving walk with Him who died and rose again that He might be our Lord.”
–John Murray, Redemption Accomplished and Applied (Grand Rapids: Eerdmans, 1955), 162-163.