1300. That “mortar” [or “clay”] signifies the good whereof the mind of the man of the church is formed, is also evident from the Word. Thus in Isaiah:

Now, O Jehovah, Thou art our Father; we are the clay and Thou our potter, and we all are the work of Thy hand (Isaiah 64:8);

“clay” denotes the man himself of the church who is being formed, and thus the good of charity, by means of which comes all the formation of man, that is, his reformation and regeneration.

In Jeremiah:

As the clay in the potter’s hand, so are we in Thy hand, the house of Israel (Jeremiah 18:6).

The meaning being similar. It is all the same whether building by means of clay, or formation, is spoken of.