'The pool of Siloam' signifies the Word in the letter, as in Isaiah 8:6, and also, generally, the pools that were in Jerusalem.

(References: Apocalypse Explained 239)

6375. 'He binds his young ass to the vine' means truth in the natural for the external Church. This is clear from the meaning of 'binding' as being joined to; from the meaning of 'the vine' as the spiritual Church, dealt with in 1069, 5113, here the external spiritual Church since the description 'the outstanding vine' immediately after means the internal church; and from the meaning of 'an ass' as truth in the natural, dealt with in 2781. From this it is evident that 'he binds his ass to the vine' means a joining through truth in the natural to the external Church.