Musnad Ahmad 32:1186

Yazid narrated to us, Hammad informed us, from Anas, who said: A group from 'Uraynah came to the Prophet, may Allah bless him and grant him peace, and they found the climate of Medina unsuitable. He mentioned the meaning of it, and he also mentioned in his hadith, Hammad said: Qatadah narrated in this hadith: "And its urine."