Musnad Ahmad 456:7

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from Salih ibn Kaysan, from 'Ubayd Allah ibn 'Abd Allah, from Zayd ibn Khalid, who said: "The Prophet, peace and blessings of Allah be upon him, led us in the morning prayer at al-Hudaybiyah following rainfall." Then he mentioned the rest of the hadith.