'Samaria,' as in Amos 4:1 and 6:1, signifies the spiritual church perverted.

(Reference: Arcana Coelestia 2220)

217. "'Behold, I stand at the door and knock.'" (3:20) This symbolically means that the Lord is present with everyone in the Word, and He presses there to be received, teaching how He can be.

Similar to this is the Lord's statement in Luke,

You yourselves (must) be like men who wait for their master, when he will return from the wedding, that when he comes and knocks they may open to him immediately. (Luke 12:36)

That a door symbolizes admittance and an entryway may be seen in no. 176 above.