Musnad Ahmad 937:103

Waki’ and Bahz narrated to us, they said: Yazid ibn Ibrahim narrated to us, from Qatadah. Bahz said: Qatadah narrated to us, from Abdullah ibn Shaqiq, who said: I said to Abu Dharr: "If I had reached the Messenger of Allah, may Allah bless him and grant him peace, I would have asked him." He said: "About what?" I said: "Did you see your Lord?" He said: "I asked him, and he said: 'Light, how could I see Him?'" Meaning, in the affirmative sense.