Musannaf Ibn Abi Shayba 16:26

Abu Bakr narrated to us, he said: Mu'tamir ibn Sulayman narrated to us, from his father, from Ibn Sirin, who said: He did not see any harm in performing the 'aqiqah (sacrifice for a newborn) before the seventh day or after it. And he used to say: "Prepare the meat of the 'aqiqah however you wish."