Musnad Ahmad 1868

It was narrated from Ibn "Abbas (رضي الله عنه) that the Messenger of Allah (ﷺ) sent eighteen sacrificial animals with a man and gave him instructions concerning them. He set out, then he came back and said: What should l do if any of them becomes too exhausted to move? He said: “Slaughter it, then dip its sandals (on its garland) in its blood, then put them on its hump, and neither you nor any of the people with you should eat from it.”