Sunan an-Nasa'i 2444

Bahz bin Hakim said:"My father told, me that my grandfather said: 'I heard the Prophet say: With regard to grazing camels, for every forty a Bint Labbun (a two-year old female camel). No differentiation is to be made between camels when calculating them. Whoever gives it seeking reward, he will be rewarded for it. Whoever refuses, we will take it, and half of his camels, as one of the rights of our Lord. And it is not permissible for the family of Muhammad to have any of them