Musnad Abu Ya'la al-Mawsili 167:12

Ishaq narrated to us, Hisham bin Yusuf narrated to us, from Ibn Jurayj, from Ibn Abi Mulaykah, that Abdullah bin al-Zubayr informed them, saying: A delegation from Banu Tamim arrived to the Prophet, may Allah bless him and grant him peace. Abu Bakr said, "Appoint al-Qa'qa' bin Ma'bad bin Zurarah [as their leader]." Umar said, "Appoint al-Aqra' bin Habis." Abu Bakr said, "You only intended to oppose me." Umar said, "I did not intend to oppose you." They argued until their voices were raised, and so [the verse] was revealed: "O you who have believed, do not put [yourselves] before Allah and His Messenger."