What are the reliable references and books that can be consulted to expand the study of backbiting (gheebah), its permissibility, and its forms, in addition to defining فسق (fisq - ungodliness/transgression), the limit of seeking redress, and giving advice?

There are many books that address backbiting and related issues, including: "Dhamm al-Gheebah wa al-Nameemah" (Censure of Backbiting and Slander) by Ibn Abi al-Dunya, chapters on backbiting from "Al-Ihya'" (The Revival) by Al-Ghazali, and from "Riyadh as-Salihin" (Gardens of the Righteous) and "Al-Adhkar" (The Remembrances) by An-Nawawi, the chapter on backbiting from "Al-Mawsoo'ah al-Fiqhiyyah" (The Fiqh Encyclopedia), and "Hurmat Ahl al-Ilm" (The Sanctity of Scholars) by Dr. Muhammad Ismail Al-Muqaddim.

These books contain definitions of seeking redress and examples thereof, as well as of immorality. Refer to Fatwas: 33108 and 59818.