Musannaf Ibn Abi Shayba 33:166

Abu Khalid al-Ahmar narrated to us, from Hajjaj, from Abu Ja'far, from Jabir, who said: The Messenger of Allah (may Allah bless him and grant him peace) passed by a dead sheep and said, "Why do you think its owners threw this away?" They said, "O Messenger of Allah, can they benefit from it when it has died?" He said, "The passing away of the world is easier to Allah than this is to its owners."