Musannaf Ibn Abi Shayba 19:5

Abu Bakr narrated to us, he said: Humayd ibn Abd al-Rahman al-Ru'asi narrated to us, from Hisham, from Abu Hazim, that Ali interceded for a thief. It was said to him, "Do you intercede for a thief?" He said, "Yes, for that is done as long as it does not reach the Imam. But if it reaches the Imam, then may Allah not pardon him if he pardons him."