Sahih Muslim 1045 d
Ibn al-Sa'di Maliki reported:
'Umar b. Khattab (Allah be pleased with him) appointed me as a collector of Sadaqa. When I had finished that (the task assigned to me) and I handed over that to him (to 'Umar), he commanded me to (accept) some remuneration (for the work). I said: I performed this duty for Allah and my reward is with Allah. He said: Take whatever has been given to you, for I also performed this duty during the time of the Messenger of Allah (ﷺ). He assigned me the task of a collector and I said as you say, and the Messenger of Allah (ﷺ) said to me: When you are given anything without your begging for it, (then accept it), eat it and give it in charity.
حَدَّثَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، حَدَّثَنَا لَيْثٌ، عَنْ بُكَيْرٍ، عَنْ بُسْرِ بْنِ سَعِيدٍ، عَنِ ابْنِ السَّاعِدِيِّ، الْمَالِكِيِّ أَنَّهُ قَالَ اسْتَعْمَلَنِي عُمَرُ بْنُ الْخَطَّابِ - رضى الله عنه - عَلَى الصَّدَقَةِ فَلَمَّا فَرَغْتُ مِنْهَا وَأَدَّيْتُهَا إِلَيْهِ أَمَرَ لِي بِعُمَالَةٍ فَقُلْتُ إِنَّمَا عَمِلْتُ لِلَّهِ وَأَجْرِي عَلَى اللَّهِ ‏.‏ فَقَالَ خُذْ مَا أُعْطِيتَ فَإِنِّي عَمِلْتُ عَلَى عَهْدِ رَسُولِ اللَّهِ صلى الله عليه وسلم فَعَمَّلَنِي فَقُلْتُ مِثْلَ قَوْلِكَ فَقَالَ لِي رَسُولُ اللَّهِ صلى الله عليه وسلم ‏
"‏ إِذَا أُعْطِيتَ شَيْئًا مِنْ غَيْرِ أَنْ تَسْأَلَ فَكُلْ وَتَصَدَّقْ ‏"‏ ‏.‏