Musnad Ahmad 27:1460

Ishaq narrated to us, Malik narrated to us, from Nafi’, from Ibn ‘Umar, that the Messenger of Allah (peace and blessings of Allah be upon him) sent a military detachment toward Najd, in which was ‘Abdullah ibn ‘Umar. Their shares were twelve camels each, and they were given an extra camel each as a reward (nafal).