A great painter once came to a prince and offered to do a fresco on a palace wall; behind him came another, who declared that he would paint on the opposite wall whatever painting the first one drew! The prince ordered a thick curtain in between the painters while they were painting. Both were commissioned to start the task. The second person finished his work the exact same moment the first one completed. The prince arrived, saw the fresco and admired it very much. Then he ordered the curtain to be removed, and lo, on the wall facing the fresco, was an exact duplicate of the picture that the first man had so laboriously painted! Exact — because the second painter polished the wall, making it a fine big mirror! Similarly, you must make your hearts clean, pure and smooth, so that the glory of the Lord might be reflected therein, and the Lord might see His own image on it.

- Divine Discourse, March 1963.