Sefer HaBahir 79

1[Rabbi Rachumai continued,] "Another interpretation: 'I have heard of Your renown; I am awed' (Habakkuk 3:2). [Meaning,] 'I understood Your renown; I am awed.' What did he understand, such that he was awed? He understood the thought of the Blessed Holy One. Just as there is no end to the thought of a person, which can carry to the end of the world, so too, the ear does not have an end and is not sated, as is written, 'The ear is not filled from hearing' (Ecclesiastes 1:8). Why is [the letter] Zayin in ear [אוזן]? Why? Because the ear is in the image of [the letter] Aleph, and Aleph> is essence of the ten utterances. Thus, 'the ear is not filled from hearing.'"