And those who accuse their wives [of adultery] and have no witnesses except themselves - then the witness of one of them [shall be] four testimonies [swearing] by Allah that indeed, he is of the truthful.
The Saheeh International Quran Translation
وَٱلَّذِينَ يَرْمُونَ أَزْوَٰجَهُمْ وَلَمْ يَكُن لَّهُمْ شُهَدَآءُ إِلَّآ أَنفُسُهُمْ فَشَهَٰدَةُ أَحَدِهِمْ أَرْبَعُ شَهَٰدَٰتٍۭ بِٱللَّهِ إِنَّهُۥ لَمِنَ ٱلصَّٰدِقِينَAnd those who accuse their wives [of adultery] and have no witnesses except themselves - then the witness of one of them [shall be] four testimonies [swearing] by Allah that indeed, he is of the truthful.