When we were ordered to give alms, we began to work as porters (to earn something we could give in charity). Abu ʿAqil came with one half of a Saʿ (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. Abu ʿAqil); 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)  

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