An-Nur 24:13

لَّوۡلَا جَآءُو عَلَيۡهِ بِأَرۡبَعَةِ شُهَدَآءَۚ فَإِذۡ لَمۡ يَأۡتُواْ بِٱلشُّهَدَآءِ فَأُوْلَـٰٓئِكَ عِندَ ٱللَّهِ هُمُ ٱلۡكَٰذِبُونَ 13

Why did they [who slandered] not produce for it four witnesses? And when they do not produce the witnesses, then it is they, in the sight of Allah, who are the liars