Is the testimony of a morally corrupt person (Fasiq) valid?
General Chapter
Al-Mughni
Book of Testimonies
Primary text
The testimony of a morally corrupt person (Fasiq) is invalid due to the command to seek witnesses of justice ('Dhawi Adl) in the Quran (Quran 65:2). It is also based on the command to verify news from a Fasiq (Quran 49:6), which implies suspension of judgment regarding their reports, and testimony is a type of report. Evidence also states that the testimony of a traitor, one limited in Islamic law (Mahdud fi al-Islam), or one holding rancor against his brother is not valid. Corruption in actions has no known dissenting view regarding the invalidation of testimony. Corruption due to belief (e.g., heresy/Bid'ah) also invalidates testimony, according to Malik, Shurayk, Ishaq, Abu Ubayd, and Abu Thawr.
Supporting text
Some scholars, like Abu Hamid among Al-Shafi'i's school, categorize divergences: disagreements over minor legal branches (Furu') do not constitute corruption. Corruption that stops short of disbelief includes cursing relatives or the Companions (like Rawafid and Khawarij), rendering testimony invalid. The third category involves disbelief (Takfir), such as denying the createdness of the Quran, invalidating testimony. Conversely, the apparent view of Al-Shafi'i, Ibn Abi Laila, Al-Thawri, and Abu Hanifa suggests that the testimony of people of deviant beliefs (Ahl al-Ahwa') is acceptable unless they explicitly endorse false testimony for one another, like the Khattabiyyah. This is justified by analogy with differences in jurisprudence among the Companions, and that their corruption stems from a perceived religious truth, unlike corruption from sinful actions.