Musannaf Ibn Abi Shayba 16:71

Abu Bakr narrated to us, he said: Abu Usama narrated to us, from Ibn 'Awn, who said: I asked al-Sha'bi about the *'Atirah* (a pre-Islamic sacrificial offering). He said: "It is forbidden; the people used to perform it." I said: "What is it?" He said: "It is in the twenty of Rajab."