Musannaf Ibn Abi Shayba 3:3482

Yazid ibn Harun narrated to us, he said: Sa'id ibn Abi 'Aruba informed us, from Qatada, from Shahr ibn Hawshab, from 'Abd al-Rahman ibn Tamim, from 'Amr ibn Kharija, that the Prophet (may Allah bless him and grant him peace) addressed them while he was upon his riding beast. He said: And his riding beast was chewing its cud, and its saliva was flowing between its shoulder blades.