Musannaf Ibn Abi Shayba 35:256

Ibn ‘Uyaynah narrated to us, from ‘Ubayd Allah ibn Abi Yazid, from his father, from Siba‘ ibn Thabit, from Umm Kurz, from the Prophet (peace and blessings of Allah be upon him), who said: "For the boy, two equivalent sheep, and for the girl, one sheep. It does not harm you whether they are male or female."