Musannaf Ibn Abi Shayba 13:3081

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: al-Mas’udi narrated to us, from ‘Abd al-Rahman ibn al-Qasim ibn Muhammad ibn Abi Bakr, from his father, he said: ‘Umar ibn al-Khattab said: "Beware, let no one be taken captive in Islam by means of false testimony, for we do not accept anyone except the upright (al-‘udul)."