Musnad Ahmad 1300:0

Narrated to us by Muhammad ibn Ja’far, narrated to us by Shu’bah, from Mansur, from Ibrahim, from ‘Alqamah, from ‘Abdullah, who said: The Messenger of Allah (peace be upon him) said: "The sacrifice for a boy is two sheep that are equivalent, and for a girl is one sheep." Narrated to us by Waki’, narrated to us by Sufyan, from ‘Asim ibn Bahdalah, from Mus’ab ibn Sa’d, from his father, from the Prophet (peace be upon him) regarding the *‘aqiqah* (sacrifice for a newborn). He said: "Two sheep for a boy and one for a girl, and it does not harm you whether they are male or female." Narrated to us by Yahya ibn Sa’id, from Hisham, he said: Narrated to me my father, from ‘Aishah, that the Messenger of Allah (peace be upon him) commanded them regarding a boy, two sheep that are equivalent, and for a girl, one sheep.