Musnad Ahmad 28:346

Waki’ narrated to us, Dawud ibn Qays al-Farra’ narrated to us, from ‘Amr ibn Shu’ayb, from his father, from his grandfather, who said: The Messenger of Allah (peace and blessings of Allah be upon him) was asked about the ‘Aqiqah (sacrifice for a newborn). He said: "I do not like disobedience (al-‘uquq). Whoever has a child born to him and would like to perform a sacrifice for him, let him do so. For the boy, two equivalent sheep, and for the girl, one sheep."