Prohibition of slander and false accusations

وَبِكُفْرِهِمْ وَقَوْلِهِمْ عَلَىٰ مَرْيَمَ بُهْتَـٰنًا عَظِيمًا

And [We cursed them] for their disbelief and their saying against Mary a great slander

يَعِظُكُمُ ٱللَّهُ أَن تَعُودُوا۟ لِمِثْلِهِۦٓ أَبَدًا إِن كُنتُم مُّؤْمِنِينَ

Allāh warns you against returning to the likes of this [conduct], ever, if you should be believers.