﴿ وَٱلَّذِينَ يَرْمُونَ أَزْوَٰجَهُمْ وَلَمْ يَكُن لَّهُمْ شُهَدَآءُ إِلَّآ أَنفُسُهُمْ فَشَهَٰدَةُ أَحَدِهِمْ أَرْبَعُ شَهَٰدَٰتٍۭ بِٱللَّهِ ۙ إِنَّهُۥ لَمِنَ ٱلصَّٰدِقِينَ ﴾

“And as for those who accuse their own wives [of adultery], but have no witnesses except them­selves, let each of these [accusers] call God four times to witness that he is indeed telling the truth,”

And those who accuse their wives of fornication but have no witnesses to substantiate this except themselves — which happened with some Companions — then the testimony of one of them fa-shahādatu ahadihim the subject shall be to testify swearing by God four times araba‘a shahādātin is in the accusative as a verbal noun that he is indeed being truthful in accusing his wife of committing fornication