An-Nur 24:6

وَٱلَّذِينَ يَرۡمُونَ أَزۡوَٰجَهُمۡ وَلَمۡ يَكُن لَّهُمۡ شُهَدَآءُ إِلَّآ أَنفُسُهُمۡ فَشَهَٰدَةُ أَحَدِهِمۡ أَرۡبَعُ شَهَٰدَٰتِۭ بِٱللَّهِ إِنَّهُۥ لَمِنَ ٱلصَّـٰدِقِينَ 6

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