Musnad Ahmad 937:183

'Arim narrated to us, Mahdi ibn Maymun narrated to us, Ghaylan narrated to us, from Shahr ibn Hawshab, from Ma'di Karib, from Abu Dharr, from the Prophet (peace and blessings of Allah be upon him), narrating from his Lord, who said: "O son of Adam, as long as you call upon Me and hope in Me, I will forgive you for what is in you. O son of Adam, if you were to meet Me with the earth full of sins, I would meet you with its equivalent in forgiveness, provided you do not associate anything with Me. O son of Adam, if you were to commit sins until your sins reached the clouds of the sky, then you sought My forgiveness, I would forgive you and I would not mind."