Musnad Ahmad 31:917

'Affan narrated to us, Hammad ibn Salamah narrated to us, Hajjaj ibn Arta'ah informed us, from 'Atiyyah ibn Sa'd, from Abu Sa'id al-Khudri, who said: The people of camels and the people of sheep boasted in the presence of the Prophet, peace and blessings of Allah be upon him. The Prophet, peace and blessings of Allah be upon him, said: "Boasting and arrogance are in the people of camels, and tranquility and dignity are in the people of sheep." And the Messenger of Allah, peace and blessings of Allah be upon him, said: "Musa, peace be upon him, was sent while he was herding sheep for his family, and I was sent while I was herding sheep for my family at Jiyad."