Musnad Abu Ya'la al-Mawsili 161:4

Ishaq ibn Abi Isra'il narrated to us, Jarir narrated to us, from Mansur, from Abu 'Uthman, from Abu Hurayrah, who said: My intimate friend and my close friend, Abu al-Qasim (may Allah bless him and grant him peace), the companion of this chamber, said: "Mercy is not removed except from a wretched person."