Musnad Ahmad 27:1904

Abu al-Yaman narrated to us, Shu'ayb narrated to us, from al-Zuhri, Salim ibn 'Abd Allah informed me, I heard 'Abd Allah ibn 'Umar saying: The Prophet, peace and blessings of Allah be upon him, set out after that, he and Ubayy ibn Ka'b, heading toward the palm trees, and he mentioned the hadith.