Musnad Ahmad 1175:2

Ibrahim ibn Ishaq narrated to us, he said: Ibn al-Mubarak narrated to me, from Usamah ibn Zayd, and Ali ibn Ishaq, he said: Abdullah narrated to us, he said: Usamah ibn Zayd informed us, from al-Fadl ibn al-Fadl, from Abd al-Rahman al-A’raj, from Duba’ah bint al-Zubayr ibn Abd al-Muttalib, that she slaughtered a sheep in her house. The Messenger of Allah (peace and blessings of Allah be upon him) sent word to her: "Feed us from your sheep." She said to the messenger: "By Allah, nothing remains with us except the neck, and I am ashamed to send the neck to the Messenger of Allah (peace and blessings of Allah be upon him)." The messenger returned and informed the Messenger of Allah (peace and blessings of Allah be upon him). He said: "Return to her and say: 'Send it, for it is the guide of the sheep, the part of the sheep closest to goodness, and the furthest of it from harm.'"