Musannaf Ibn Abi Shayba 24:105

Mu'awiyah ibn Hisham narrated to us, from Sufyan, from Abu Ishaq, who said: I saw Hujr ibn 'Adi, and he was saying: "My pledge of allegiance, I will not revoke it, nor will I ask to be released from it, let Allah and the people bear witness." He meant by his statement: Al-Mughirah.