صحيح ابن خزيمه
Sahih Ibn Khuzaymah
جماع أبواب قسم الصدقات وذكر أهل سهمانها
Chapters on Distribution of Zakat and its Recipients
(75) باب ذكر الدليل على أن الصدقة المحرمة على النبى صلى الله عليه وسلم هي الصدقة المفروضة التى أوجبها الله فى أموال الأغنياء لأهل سهمان الصدقة، دون صدقة التطوع
75| Chapter on the evidence that the zakat forbidden to the Prophet is the obligatory zakat, not voluntary charity
And in the narration of Hazrat Abdul Muttalib bin Rabee’ah as well (there is clarification of the obligatory zakat) when he, along with Sayyiduna Fadl bin Abbas (may Allah be pleased with them both), presented himself before the Noble Prophet (peace and blessings be upon him) and requested to be appointed as collectors over the zakat, and the Noble Prophet (peace and blessings be upon him) informed both of them that this zakat is the impurity of the people and this wealth is not lawful for Muhammad (peace and blessings be upon him) and his family, and indeed they had requested to be appointed as collectors over the obligatory zakat. Therefore, the Noble Prophet (peace and blessings be upon him) giving them this answer, that this charity for which you have asked me to appoint you as collectors, it is the impurity of the people and this wealth is not lawful for Muhammad (peace and blessings be upon him) and his family.
تخریج الحدیث: تقدم۔۔۔