Surah At-Taubah (The Repentance), Verse 79

اَلَّذِیْنَ یَلْمِزُوْنَ الْمُطَّوِّعِیْنَ مِنَ الْمُؤْمِنِیْنَ فِی الصَّدَقٰتِ وَالَّذِیْنَ لَا یَجِدُوْنَ اِلَّا جُهْدَهُمْ فَیَسْخَرُوْنَ مِنْهُمْ سَخِرَ اللّٰهُ مِنْهُمْ وَلَهُمْ عَذَابٌ اَلِیْمٌ ۟

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 slander such of the believers as give themselves freely to (deeds of) charity, as well as such as can find nothing to give except the fruits of their labour,- and throw ridicule on them,- Allah will throw back their ridicule on them: and they shall have a grievous penalty.”

Quran 9:79 (Yusuf Ali Translation)