Musannaf Ibn Abi Shayba 33:164

Muhammad ibn Mus’ab narrated to us, he said: Al-Awza’i narrated to us, from Al-Zuhri, from ‘Ubaydullah, from Ibn ‘Abbas, that the Prophet (peace and blessings of Allah be upon him) passed by a dead sheep that its owners had cast away. He said: "The passing away of the world is easier to Allah than this [sheep] was to its owners."