'Jericho' generally signifies the good of truths.

In Luke 10:30, this signifies the church in possession of the knowledges of truth and good.

In Joshua 6:1, 'Jericho' signifies instruction and the good of life because no one can be instructed in the truths of doctrine but he who is in the good of life. In an opposite sense, it signifies the profanation of truth and good. (Apocalypse Explained 700)

(References: Luke 10)