وَالَّذينَ يَرمونَ أَزواجَهُم وَلَم يَكُن لَهُم شُهَداءُ إِلّا أَنفُسُهُم فَشَهادَةُ أَحَدِهِم أَربَعُ شَهاداتٍ بِاللَّهِ ۙ إِنَّهُ لَمِنَ الصّادِقينَ

If a man accuses his wife, but has no witnesses except himself, he must swear by God four times that he is truthful.