Sayyiduna Ibn al-Sa'idi al-Maliki (may Allah be pleased with him) said: Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) appointed me over the charity. When I had finished with it and handed it over to him, he ordered a wage for me. I said: I only worked for Allah and His Messenger, and my reward is with Allah. He said: Take what you are given, for I worked in the time of the Messenger of Allah (peace and blessings be upon him), and he paid me a wage, and I said the like of what you have said. So the Messenger of Allah (peace and blessings be upon him) said to me: "When you are given something without asking for it, then eat (from it) and give charity."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الصدقات / 13169