The Messenger of Allah ﷺ said, "For a boy, two sheep are to be sacrificed, and for a girl, one sheep."
قال رسول الله ﷺ: عن الغلام شاتان، وعن الجارية شاة.
Abu Dawud (2836) and Ahmad (27143) both narrated it from the hadith of Hammad bin Zayd, from Ubaydullah bin Abu Yazid, from Sibaa bin Thabit, from Umm Kurz, and I have already related it. All its narrators are trustworthy except Sibaa bin Thabit. Ibn Hibban mentioned him in Thiqat Tabiin (4/348), and Ibn Saad said, "He narrated from Umar bin Khattab and had few hadiths." Dhahabi said, "He is hardly known." However, Hafiz said in Tahdhib (3/452), "Abu Qasim Baghawi and Ibn Qani mentioned him among the Companions and both cited his hadith, 'I witnessed from the time of pre-Islamic ignorance that they used to circle between Safa and Marwa,'" the hadith. "But it is mawquf, so he would be among the mukhadramun, or rather among the Companions, for a reason I mentioned in my book on the Companions." End of quote.I say, he devoted an entry to him in the first section of Isaba (2/13), and cited for him the aforementioned report, then said, "The evidence for his companionship from this is what was mentioned earlier, that no Qurayshi remained in Makkah except that he witnessed the Farewell Pilgrimage with the Prophet ﷺ, and this man was a Qurayshi who witnessed the pre-Islamic era and remained afterward until Ubaydullah bin Abu Yazid heard from him, and he is among the junior tabiin." End of quote.Accordingly, if his companionship is established then the chain is sahih, and otherwise it has support from another narration. Abu Dawud (2834), Nasai (4216), and Imam Ahmad (27142) narrated it through various routes from Sufyan bin Uyayna, from Amr bin Dinar, from Ataa (that is, Ibn Abu Rabah), from Habiba bint Maysara, from Umm Kurz Kabiyya, who said, I heard the Messenger of Allah ﷺ say, "For a boy, two equivalent sheep, and for a girl, one sheep."Ibn Hibban (5313) narrated it through the route of Abdul-Razzaq, and it is in his Musannaf (7953), from Ibn Jurayj, who said, Ataa informed me, with the same wording, and he added, "So I said to him," meaning Ataa, "'What does equivalent mean?' He said, 'Two that are alike, its males being more preferable to him than its females.'" Its narrators are trustworthy except for Habiba bint Maysara, from whom only Ataa transmitted alone, and no one deemed her trustworthy except Ibn Hibban, by mentioning her among the trustworthy (4/194). For this reason Hafiz said, "Acceptable," meaning when corroborated, and she has indeed been corroborated, Sibaa bin Thabit corroborated her as mentioned before.A note of caution, the hadith of Sibaa bin Thabit from Umm Kurz was also narrated by Sufyan bin Uyayna, but he added a man to its chain. What Abu Dawud (2835), Ibn Majah (3162), and Imam Ahmad (27139) narrated, and Ibn Hibban (5312) and Hakim (4/237-238) graded sahih, all of them through various routes from Sufyan bin Uyayna, from Ubaydullah bin Abu Yazid, from his father, from Sibaa bin Thabit, with the same wording. They added, all except Ibn Majah, "It will not harm you whether they are males or females." Abu Dawud, Ahmad, and Hakim added another hadith, which is his saying ﷺ, "Leave the birds in their resting places." Hakim said, "Its chain is sahih."However, the leading scholars judged this narration of Sufyan to contain an error. Imam Ahmad said in his Musnad, following this hadith, and he had already related two other hadiths for him with the same chain, he said, "Sufyan errs in these hadiths, Ubaydullah heard them from Sibaa bin Thabit." Likewise Abu Dawud Sijistani said, following the hadith of Hammad bin Zayd, "This is the hadith, and the hadith of Sufyan is an error."In Hafiz Mizzi's copy, as found in Tuhfat Ashraf (13/99), he said, "This hadith is the correct one, and the hadith of Sufyan is a mistake." See further documentation in Minna Kubra (4/525).