Ba'al Shem Tov, Noach 21/בעל שם טוב על התורה·נח כ״א

1My grandfather of blessed memory explained the secret of the verse (Genesis 6:16) "lower and second and third decks" - that one should make ones petitions from the letters, from the mystery of the divine light that dwells within them, and make the petition come from there, etc.