Surah An-Nur, ayah 6

وَٱلَّذِينَ يَرۡمُونَ أَزۡوَٰجَهُمۡ وَلَمۡ يَكُن لَّهُمۡ شُهَدَآءُ إِلَّآ أَنفُسُهُمۡ فَشَهَٰدَةُ أَحَدِهِمۡ أَرۡبَعُ شَهَٰدَٰتِۭ بِٱللَّهِ إِنَّهُۥ لَمِنَ ٱلصَّٰدِقِينَ ٦

Walladhīna yarmūna azwājahum walam yakul lahum shuhadā'u illā anfusuhum fashahādatu ahadihim arba'u shahādāti billāhi innahū laminas-sādiqīn

And those who accuse their wives [of adultery] and have no witnesses except themselves - then the witness of one of them⁹⁷⁶ [shall be] four testimonies [swearing] by Allāh that indeed, he is of the truthful.