Revelation 21:27: And there shall in no wise enter into it any thing that defileth, neither whatsoever worketh abomination, or maketh a lie: but they which are written in the Lamb's book of life.

Revelation 21:27 confirms the doctrine that no unclean thing¹ can enter the kingdom of heaven.² Any thing that defileth³ means all things common or unclean.⁴ The word abomination describes a wide range of sins from ceremonial impurity to the very grossest kinds of immorality, evil, and idol worship.⁵ People that maketh a lie are hypocrites, including idol worshippers in particular.⁶ These three classes of sinners represent all people who shall in nowise, or by no means,⁷ enter the holy city Jerusalem as a symbol of the celestial kingdom.⁸ They will suffer a measure of spiritual death in a lesser kingdom of glory⁹ because they cannot enter the celestial kingdom where the light and glory of the Father and the Son are present in their fulness.¹⁰

Only they which are written in the Lamb's book of life¹¹ gain entry into the celestial kingdom.¹² To be more specific, however, the Lamb's book of life contains the names of those that qualify for exaltation in the celestial kingdom.¹³ Unexalted people may also enter the celestial kingdom, but they do so as angels.¹⁴ The Lamb's book of life, here and elsewhere, contains only the names of exalted saints. John consistently describes exaltation-worthy saints as those that enter the celestial kingdom.¹⁵

These sayings are faithful and true: and the Lord God of the holy prophets sent his angel to shew unto his servants the things which must shortly be done. Behold, I come quickly: blessed is he that keepeth the sayings of the prophecy of this book.

— Revelation 22:6-7