'A lip' in general signifies doctrine.

In Isaiah 6:3, 7, this signifies the interior parts of a person and thus internal worship where adoration is grounded.

In Isaiah 37:29, this signifies the thought of the understanding

In Malachi 2:6, 7, this denotes doctrine grounded in charity.

(Referencias: Arcana Coelestia 1284, Arcana Coelestia 1288)

'A watchman,' as in Isaiah 21:11, in an internal sense, signifies someone who observes the states of the church and its changes, which applies to every prophet.

(Referencias: Arcana Coelestia 10144)