Lying about People
Imām Ibn Taimiyyah, may Allāh have mercy on him, said:
Lying about a person, [any lying], is impermissible, whether that [person] were a Muslim or a disbeliever, a righteous person or an evil-doer. However, making false claims or fabrications against a believer is worse in severity.
Majmūʿ Al-Rasāʾil wa-l-Masāʾil, vol. 5, p. 105.