Sunan an-Nasai Book 23, Hadith 2444

أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا يَحْيَى، قَالَ حَدَّثَنَا بَهْزُ بْنُ حَكِيمٍ، قَالَ حَدَّثَنِي أَبِي، عَنْ جَدِّي، قَالَ سَمِعْتُ النَّبِيَّ صلى الله عليه وسلم يَقُولُ ‏ "‏ فِي كُلِّ إِبِلٍ سَائِمَةٍ فِي كُلِّ أَرْبَعِينَ ابْنَةُ لَبُونٍ لاَ يُفَرَّقُ إِبِلٌ عَنْ حِسَابِهَا مَنْ أَعْطَاهَا مُؤْتَجِرًا فَلَهُ أَجْرُهَا وَمَنْ أَبَى فَإِنَّا آخِذُوهَا وَشَطْرَ إِبِلِهِ عَزْمَةٌ مِنْ عَزَمَاتِ رَبِّنَا لاَ يَحِلُّ لآلِ مُحَمَّدٍ صلى الله عليه وسلم مِنْهَا شَىْءٌ ‏"‏ ‏.‏

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