Musannaf Ibn Abi Shayba 33:311

Abu Khalid al-Ahmar narrated to us, from Dawud, from al-Sha'bi, who said: Abdullah said: "Verily, I do not fear for you regarding mistakes, but I fear for you regarding intentional acts. Verily, I do not fear for you that you will consider your deeds few, but I fear for you that you will consider them many."