Musnad Ahmad 30:3226

Muhammad ibn Ja‘far narrated to us, he said: Ma‘mar narrated to us, he said: Ibn Shihab informed us, from Ibn al-Musayyib, from Abu Hurayrah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "There is no *Fara‘* and no *‘Atirah*." Ibn Shihab said: "The *Fara‘* was that the people of the Pre-Islamic Era (Jahiliyyah) would slaughter the first offspring that their livestock produced. And the *‘Atirah* was a sacrifice in the month of Rajab."