Q 7: A person incited another to
be hostile towards someone else; defaming and slandering him and even worse bearing a false witness against him.
Is it permissible for the wronged and oppressed man to make a Du`a' (supplication) in his Salah (Prayer) that calamity and disease befall the oppressors, or that they become childless?
(Part No. 24; Page No. 257
Giving false witness is one of the major sins. You are permitted to supplicate to Allah (Glorified and Exalted be He) to avenge them; but if you pardon them, it would be much better.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.