Revelation 3:1–6 comprises the letter Jesus dictated to John to send to the church in Sardis. The church’s reputation was a far cry from reality. It had a reputation of being a live church, but actually it was dead. While this reputation is—technically—a praise, it’s a hollow one. Jesus instructed this church to wake up and strengthen what remained. All was not lost, though. A few members of the church were true to the faith, and Jesus promised they would walk with Him in purity. He would also keep their names in the book of life and confess their names before His Father.
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“Revelation 3:5” Bibleref.com
5 He who overcomes will be arrayed in white garments, and I will in no way blot his name out of the book of life, and I will confess his name before my Father, and before his angels.