925. But only those who are written in the Lamb's Book of Life. This symbolically means that the only people received into the New Church, or New Jerusalem, are those who believe in the Lord and live in accordance with His commandments in the Word.

That this is the symbolic meaning of being written in the Book of Life may be seen in no. 874 above, and there is no need to add more here.

In Revelation 21:20, 'an unclean thing' signifies spiritual whoring, which is the adulteration of good, and falsification of truth of the Word. This is uncleanness and impurity itself, because the Word is cleanness and purity itself, and it is defiled by evils and falsities when it is perverted.

(Odkazy: Apocalypse Revealed 924)