'Vanity' signifies evil and the falsity of evil. 'Vanities of strangers' signify falsities of religion.

In Exodus 5:9, vain words signify truths when said by people who believe falsities. (Arcana Coelestia 7122)

(References: Apocalypse Explained 340)

6355. 'In their congregation let not my glory be united' means that neither does the truth of spiritual good have any wish to know the resulting false ideas constituting their thought. This is clear from the representation of Israel as spiritual good, dealt with in 6340; from the meaning of 'in their congregation let it not be united' as having no wish to be joined to the false ideas constituting their thought or thus to know them (false ideas constituting a person's thought are meant by 'congregation', for 'a congregation', like 'a multitude', is used with reference to truths, and in the contrary sense to falsities); and from the meaning of 'glory', which is used with reference to truth, dealt with in 4809, 5922, for to those who cherish spiritual good truth is glory.