Musnad Ahmad 1018:137

Abu al-Nadr narrated to us, Abu Mu’awiyah—meaning Shayban—narrated to us, from Layth, from Shahr ibn Hawshab, who said: The Ansari, the companion of the sacrificial animals of the Messenger of Allah (peace and blessings of Allah be upon him), narrated to me that when the Messenger of Allah (peace and blessings of Allah be upon him) sent him, he said: I returned and said: "O Messenger of Allah, what do you command me to do with that which is dying among them?" He said: "Slaughter it, then dip its sandal in its blood, then place it on its side or on its flank, and do not eat from it, neither you nor anyone from the people of your company."