So that Christ may dwell in your hearts through faith; and that you, being rooted and grounded in love, (Eph. 3:17 NASB) Christ lives in us—that is the mystery of mysteries in the New Testament. He has become united as one with His Church, which is His Body. Paul prayed in the scripture above that
Christ in you
“I have been crucified with Christ; and it is no longer I who live, but Christ lives in me; and the life which I now live in the flesh I live by faith in the Son of God, who loved me, and delivered Himself up for me. (Gal. 2:19 NAS) It will definitely come as
I have been crucified with Christ and I no longer live, but Christ lives in me. The life I now live in the body, I live by faith in the Son of God, who loved me and gave himself for me. (Gal. 2:19 NIV) Christianity is Christ living His life in and through a believer.