Musnad Ahmad 245:1

'Affan narrated to us, Aban al-'Attar narrated to us, Qatadah narrated to us, from Shahr ibn Hawshab, from Abu 'Ubayd, that he cooked a pot for the Messenger of Allah, peace and blessings of Allah be upon him, in which there was meat. The Messenger of Allah, peace and blessings of Allah be upon him, said: "Hand me its foreleg." So I handed it to him. Then he said: "Hand me its foreleg." So I handed it to him. Then he said: "Hand me its foreleg." He (Abu 'Ubayd) said: "O Prophet of Allah, how many forelegs does a sheep have?" He said: "By the One in Whose hand is my soul, had you remained silent, it would have continued to give you a foreleg for as long as you called for it."