Andrew Purves, Reconstruction Pastoral Theology (pg. 84)
To be clear: union with Christ does not lead to an imitation of Christ, a life spent following Jesus’ example in the hope that we will become better people. The Christian life is not to be understood as obedience to either an ethical imperative or a spiritual ideal. Rather, the Christian life is the radical and converting participation in Jesus Christ’s own being and life, and thus a sharing in his righteousness, holiness, and mission through the bond of the Holy Spirit.
Note, too, the emphasis I place on the work of the Holy Spirit. Union with Christ is entirely a work of God. Our human acts, beliefs, and decisions are powerless to effect a relationship with God. John Calvin understood that our deepest self had to become reconfigured and reconstituted or, to use his words, “regenerated” or “vivified,” through related to Jesus Christ. … God must reorder us be turning us in a new direction be uniting us to Jesus. So our being and becoming Christian is a divine initiative and not something that can be worked out through heightened religiosity, morality, activity, will, or spirituality. We are conjoined to Christ by the unilateral work of God though the Holy Spirit – to effect what Calvin called a “mystical union.”