Sahih Al Bukhari (588)

عن أبي حميد الساعدي قال "استعمل النبي (صلى الله عليه وسلم) رجلا من الأزد يقال له ابن الأتبية على الصدقة فلما قدم قال هذا لكم وهذا أهدي لي قال فهلا جلس في بيت أبيه أو بيت أمه فينظر يهدى له أم لا والذي نفسي بيده لا يأخذ أحد منه شيئا إلا جاء به يوم القيامة يحمله على رقبته إن كان بعيرا له رغاء أو بقرة لها خوار أو شاة تيعر ثم رفع بيده حتى رأينا عفرة إبطيه اللهم هل بلغت اللهم هل بلغت ثلاثا"

Abu Humayd As-Sa`idy narrated that the Prophet (peace be upon him) appointed a man from the tribe of Al-Azd, called Ibn `Utbiyya for collecting the Zakat. When he returned he said: "This (i.e. the Zakat) is for you and this has been given to me as a present." The Prophet (peace be upon him) said: "Why hadn't he stayed in his father's or mother's house to see whether he would be given presents or not? By Him in Whose Hands my life is, whoever takes something from the resources of the Zakat (unlawfully) will be carrying it on his neck on the Day of Resurrection; if it be a camel, it will be grunting; if a cow, it will be mooing; and if a sheep, it will be bleating." The Prophet (peace be upon him) then raised his hands till we saw the whiteness of his armpits, and he said thrice: "O Allah! Haven't I conveyed Your Message (to them)?"