Musnad Ahmad 937:105

Waki’ narrated to us, al-A’mash narrated to us, from Mujahid, from ‘Abd al-Rahman ibn Abi Layla, from Abu Dharr, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said. And Ya’la narrated to us, al-A’mash narrated to us, from Shahr ibn Hawshab, from ‘Abd al-Rahman ibn Ghanam, from Abu Dharr, he said: The Messenger of Allah (peace and blessings of Allah be upon him) said to me: "Shall I not guide you to a treasure from the treasures of Paradise? There is no power and no strength except by Allah."