Musnad Abu Ya'la al-Mawsili 7:10

Wahb ibn Baqiyyah al-Wasiti narrated to us, Khalid narrated to us, from Abd al-Rahman ibn Ishaq, from al-Zuhri, from Muhammad ibn Jubayr ibn Mut'im, from Abd al-Rahman ibn Awf, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "I witnessed, while I was a young boy, an alliance (Hilf) with my paternal uncles, the Mutayyibin (the Scented Ones). I would not love to have red camels in exchange for breaking it."