ٱلَّذِينَ يَلْمِزُونَ ٱلْمُطَّوِّعِينَ مِنَ ٱلْمُؤْمِنِينَ فِى ٱلصَّدَقَـٰتِ وَٱلَّذِينَ لَا يَجِدُونَ إِلَّا جُهْدَهُمْ فَيَسْخَرُونَ مِنْهُمْ ۙ سَخِرَ ٱللَّهُ مِنْهُمْ وَلَهُمْ عَذَابٌ أَلِيمٌ
Allazeena yalmizoonal mut tawwi'eena minalmu'mineena fis sadaqaati wallazeena laa yajidoona illaa juhdahum fayaskharoona minhum sakhiral laahu minhum wa lahum azaabun aleem
Those who malign the believers who give freely in charity, and mock those who find nothing to give but their own effort — God mocks them, and a painful punishment awaits them.
Muṭṭawwiʿīn names those who give beyond what is asked of them, and juhd is a person's utmost capacity — so both parties mocked here had given all they had, one from surplus and one from a day's labour. Lamz is fault-finding by gesture and innuendo, the sidelong dig, from the same root that names the sneerers in surah 104. Commentators treat the answering mockery as a figure of speech, the reply cast in the language of the offence.