A.T. Robertson Commentary Revelation 21:27

"and there shall in no wise enter into it anything unclean, or he that maketh an abomination and a lie: but only they that are written in the Lamb`s book of life." — Revelation 21:27 (ASV)

There shall in no wise enter into it (ου μη εισελθη εις αυτην). Double negative again with the second aorist active subjunctive of εισερχομα with εις repeated. Like Isa 52:1; Ezekiel 44:9.

Anything unclean (παν κοινον). Common use of παν with negative like ουδεν, and the use of κοινος for defiled or profane as in Mr 7:2; Acts 10:14, not just what is common to all (Titus 1:4).

Or he that (κα ο). "And he that."

Maketh an abomination and a lie (ποιων βδελυγμα κα ψευδος). Like Babylon (17:4 which see for βδελυγμα) and 21:8 for those in the lake of fire and brimstone, and 22:15 for "every one loving and doing a lie." These recurrent glimpses of pagan life on earth and of hell in contrast to heaven in this picture raise the question already mentioned whether John is just running parallel pictures of heaven and hell after the judgment or whether, as Charles says: "The unclean and the abominable and the liars are still on earth, but, though the gates are open day and night, they cannot enter." In apocalyptic writing literalism and chronology cannot be insisted on as in ordinary books. The series of panoramas continue to the end.

But only they which are written (ε μη ο γεγραμμενο). "Except those written." For "the book of life" see 3:5; 13:8; 20:15. Cf. Daniel 12:1.