Once Rabbi Shimon ben Yehozedek addressed Rabbi Sh'muel ben Nachman and
said, "I hear that thou art a Baal Aggadah; canst thou therefore tell me
whence the light was created?" "We learn," he replied in a whisper,
"that God wrapped Himself with light as with a garment, and He has
caused the splendor thereof to shine from one end of the world to the
other." The other said, "Why whisperest thou, I wonder, since Scripture
says so plainly (Ps. civ. 2) 'Who covereth Himself with light as with a
garment'?" The reply was, "I heard it in a whisper, and in a whisper I
have told it to thee."
THE MIDRASHIM, _Bereshith Rabbah_, chap. 3.