Surah An-Nur, ayah 4

وَٱلَّذِينَ يَرۡمُونَ ٱلۡمُحۡصَنَٰتِ ثُمَّ لَمۡ يَأۡتُواْ بِأَرۡبَعَةِ شُهَدَآءَ فَٱجۡلِدُوهُمۡ ثَمَٰنِينَ جَلۡدَةٗ وَلَا تَقۡبَلُواْ لَهُمۡ شَهَٰدَةً أَبَدٗاۚ وَأُوْلَٰٓئِكَ هُمُ ٱلۡفَٰسِقُونَ ٤

Walladhīna yarmūnal-muhsanāti thumma lam ya'tū bi arba'ati shuhadā'a fajlidūhum thamānīna jaldatan walā taqbalū lahum shahādatan abadan wa ulā'ika humul-fāsiqūn

And those who accuse chaste women and then do not produce four witnesses - lash them with eighty lashes and do not accept from them testimony ever after. And those are the defiantly disobedient,