Sahih Bukhari Volume 6, Book 65, Hadith 4670

حَدَّثَنِي بِشْرُ بْنُ خَالِدٍ أَبُو مُحَمَّدٍ، أَخْبَرَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، عَنْ شُعْبَةَ، عَنْ سُلَيْمَانَ، عَنْ أَبِي وَائِلٍ، عَنْ أَبِي مَسْعُودٍ، قَالَ لَمَّا أُمِرْنَا بِالصَّدَقَةِ كُنَّا نَتَحَامَلُ فَجَاءَ أَبُو عَقِيلٍ بِنِصْفِ صَاعٍ، وَجَاءَ إِنْسَانٌ بِأَكْثَرَ مِنْهُ، فَقَالَ الْمُنَافِقُونَ إِنَّ اللَّهَ لَغَنِيٌّ عَنْ صَدَقَةِ هَذَا، وَمَا فَعَلَ هَذَا الآخَرُ إِلاَّ رِئَاءً‏.‏ فَنَزَلَتْ ‏{‏الَّذِينَ يَلْمِزُونَ الْمُطَّوِّعِينَ مِنَ الْمُؤْمِنِينَ فِي الصَّدَقَاتِ وَالَّذِينَ لاَ يَجِدُونَ إِلاَّ جُهْدَهُمْ‏}‏ الآيَةَ‏

Narrated By Abu Musud : When we were ordered to give alms, we began to work as porters (to earn something we could give in charity). Abu Uqail came with one half of a Sa (special measure for food grains) and another person brought more than he did. So the hypocrites said, "Allah is not in need of the alms of this (i.e. 'Uqail); and this other person did not give alms but for showing off." Then Allah revealed: 'Those who criticize such of the Believers who give charity voluntarily and those who could not find to give in charity except what is available to them.' (9.79)