"For every teacher, when he accepts any earthly hearer of the teaching of the heavenly words, takes a tile. When he has begun to speak to him of the recompense of the Heavenly Kingdom, the vision of supernal peace, he draws the city of Jerusalem on the tile. He lays this before him because with intent mind he considers the quality of the hearer, i.e. he perceives him as advanced or enfeebled, and moderates the words of his preaching to fit his understanding, so that the city of Jerusalem, i.e. the vision of peace, can be drawn in the mind of the hearer. Therefore it may be said, 'Take thee a tile,' viz. the earthly heart of a neighbor. 'And lay it before thee,' surely so that you may guard his life and understanding with an intent mind. 'And draw upon it the city of Jerusalem,' so that it may become clear to him what are the heavenly joys of inward peace, and to strive after the perception of the glory of the Heavenly Kingdom."
Gregory the Great, Homilies on the Book of the Prophet Ezekiel I.12.23