كتاب الزكاة
12  
The Book of Zakat
(21)
Chapter: Carrying goods for payment and giving charity out of one's wages, and the stern prohibition of belittling the one who gives something small in charity
(21)
باب الْحَمْلِ بِأُجْرَةٍ يُتَصَدَّقُ بِهَا وَالنَّهْىِ الشَّدِيدِ عَنْ تَنْقِيصِ الْمُتَصَدِّقِ بِقَلِيل
Sahih Muslim 1018 a

Abu Mas'ud reported:

We were commanded to give charity (despite the fact.) that we were coolies. Abu 'Aqil donated half a sa'. And there came another man with more than this. The hypocrites said: Verily Allah does not stand in need of the charity of this, and the second one has done nothing but only made a show (of his charity). Then this verse was revealed." Those who scoff at the voluntary givers of charity among the believers as well as those who cannot find anything (to give) but with their hard labour" (ix. 80). And Bishr did not utter the word Muttawwi'in.
حَدَّثَنِي يَحْيَى بْنُ مَعِينٍ، حَدَّثَنَا غُنْدَرٌ، حَدَّثَنَا شُعْبَةُ، ح وَحَدَّثَنِيهِ بِشْرُ بْنُ خَالِدٍ، - وَاللَّفْظُ لَهُ - أَخْبَرَنَا مُحَمَّدٌ، - يَعْنِي ابْنَ جَعْفَرٍ - عَنْ شُعْبَةَ، عَنْ سُلَيْمَانَ، عَنْ أَبِي وَائِلٍ، عَنْ أَبِي مَسْعُودٍ، قَالَ أُمِرْنَا بِالصَّدَقَةِ ‏.‏ قَالَ كُنَّا نُحَامِلُ - قَالَ - فَتَصَدَّقَ أَبُو عَقِيلٍ بِنِصْفِ صَاعٍ - قَالَ - وَجَاءَ إِنْسَانٌ بِشَىْءٍ أَكْثَرَ مِنْهُ فَقَالَ الْمُنَافِقُونَ إِنَّ اللَّهَ لَغَنِيٌّ عَنْ صَدَقَةِ هَذَا وَمَا فَعَلَ هَذَا الآخَرُ إِلاَّ رِيَاءً فَنَزَلَتْ ‏{‏ الَّذِينَ يَلْمِزُونَ الْمُطَّوِّعِينَ مِنَ الْمُؤْمِنِينَ فِي الصَّدَقَاتِ وَالَّذِينَ لاَ يَجِدُونَ إِلاَّ جُهْدَهُمْ‏}‏ وَلَمْ يَلْفِظْ بِشْرٌ بِالْمُطَّوِّعِينَ ‏.‏
Reference : Sahih Muslim 1018a
In-book reference : Book 12, Hadith 92
USC-MSA web (English) reference : Book 5, Hadith 2223
  (deprecated numbering scheme)