Q.
But why art thou called a Christian?
A.
Because I am a member of Christ by faith, and thus am partaker of his anointing; that so I may confess his name, and present myself a living sacrifice of thankfulness to him: and also that with a free and good conscience I may fight against sin and Satan in this life and afterwards I reign with him eternally, over all creatures.Heidelberg Catechism, Lord’s Day 12, Question 32.
from Daily Confession
We live like Christ because we are in Christ.
Baptism into the name of the Father, Son and Holy Spirit signifies a union with God, not a decision to live according to God’s rules.
Our identity flows from our union with Him, not from our emulation of His life.
“The union between Christ and his mystical members is firm and indissoluble. Were it so that the believer only apprehended Christ—but Christ not apprehended him, we could promise little as the stability of such a union; it might quickly be dissolved: but as the believer apprehends Christ by faith—so Christ apprehends him by his Spirit—and none shall pluck him out of his hand.
Did the child only keep hold of the nurse, it might at length grow weary, and let go its hold, and so fall away: but if the nurse has her arms about the child, it is in no hazard of falling away, even though it be not actually holding by her. So, whatever sinful intermissions may happen in the exercise of faith; yet the union remains sure, by reason of the constant indwelling of the Spirit.”
—Thomas Boston, “Mystical Union”, Human Nature in Its Fourfold State (Edinburgh: Banner of Truth, 1964)
Of First Importance