Musnad Ahmad 28:462

Yazid narrated to us, Al-Hajjaj and Ma'mar ibn Sulayman al-Raqqi informed us, from Al-Hajjaj ibn Artah, from 'Amr ibn Shu'ayb, from his father, from his grandfather, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The testimony of a treacherous person is not permissible, nor [the testimony of] one who has been punished with a prescribed punishment (hadd) in Islam, nor [the testimony of] one who holds a grudge against his brother."