Musannaf Ibn Abi Shayba 33:1128

Muhammad ibn Abd Allah al-Zubayri narrated to us, from Sufyan, from Musa ibn Abi ‘Aisha, from Sa‘id ibn Jubayr regarding the saying of Allah, the Exalted: "Nay, man will be a witness against himself," he said: A witness against himself, even if he offers excuses.