Musnad Ahmad 27:839

'Abd al-Rahman narrated to us, Malik narrated to us, from Nafi', from Ibn 'Umar: "The Messenger of Allah (peace and blessings of Allah be upon him) sent a military detachment toward Najd. They obtained much camel booty, and their shares reached eleven camels or twelve camels, and they were given an extra camel each as a reward (nafal)."