Musnad Ahmad 937:61

Yahya ibn Hammad narrated to us, Abu 'Awanah narrated to us, from Abu Bishr, from Talq ibn Habib, from Bashir ibn Ka'b al-'Adawi, from Abu Dharr, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said to me: "Do you have an interest in a treasure from the treasures of Paradise?" I said: "Yes." He said: "There is no power and no strength except by Allah (la hawla wa la quwwata illa billah)."