An Nasai: Hadith 4158

"O Messenger of Allah! (What about) the Fara'?" He said: "It is a duty, but if you leave it (the animal) until it becomes half-grown and you load upon it (in Jihad) in the cause of Allah or give it to a widow, that is better than if you slaughter it (when it is just born) and its flesh is difficult to separate from its skin, then you turn your vessel upside down (because you will no longer be able to get milk from the mother) and you cause your she-camel to grieve (at the loss of its young)." They said: "O Messenger of Allah, (what about) the 'Atirah?" He said: "The 'Atirah is a duty."

Abu 'Abdur-Rahman (An-Nasa'i) said: Abu 'Ali Al-Hanafi (one of the narrators); they are four brothers: One of them is Abu Bakr, and Bishr, and Sharik, and the other.