Musnad Abu Ya'la al-Mawsili 252:23

Mus'ab ibn 'Abd Allah al-Zubayri narrated to us, he said: My father narrated to me, from Qudamah ibn Ibrahim, who said: I saw al-Hajjaj striking 'Abbas ibn Sahl regarding the affair of Ibn al-Zubayr. Then Sahl ibn Sa'd came to him, and he was an old man with two braids, wearing two garments: a lower garment and a mantle. He stood between the two rows and said: "O Hajjaj, do you not observe regarding us the bequest of the Messenger of Allah, may Allah bless him and grant him peace?" He said: "And what did the Messenger of Allah, may Allah bless him and grant him peace, bequeath regarding you?" He said: "He bequeathed that the doer of good among the Ansar should be treated well, and the wrongdoer among them should be pardoned." He said: "So he released him."