Musannaf Ibn Abi Shayba 33:261

Waki’ narrated to us, from Usama, from al-Zuhri, from Humayd ibn ‘Abd al-Rahman, who said: ‘Umar said: "If a lamb from the offspring of the sheep were to perish due to neglect on the bank of the Euphrates, I would fear that Allah would question me about it."