النّور — An-Nur Ayat 6
وَالَّذِيْنَ يَرْمُوْنَ اَزْوَاجَهُمْ وَلَمْ يَكُنْ لَّهُمْ شُهَدَاۤءُ اِلَّآ اَنْفُسُهُمْ فَشَهَادَةُ اَحَدِهِمْ اَرْبَعُ شَهٰدٰتٍۢ بِاللّٰهِ ۙاِنَّهٗ لَمِنَ الصّٰدِقِيْنَ
Wal-lażīna yarmūna azwājahum wa lam yakul lahum syuhadā'u illā anfusuhum fa syahādatu aḥadihim arba‘u syahādātim billāh(i), innahū laminaṣ-ṣādiqīn(a).
"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."