The fabricators fall into several categories. The most harmful of them are those regarded as ascetics who, imagining that they were acting out of devotion, forged reports; their fabrications were accepted because people trusted them. The Karramiyyah even deemed fabrication permissible in matters of targhīb (encouragement) and tarhīb (warning), a view that flatly contradicts the consensus of all reputable Muslims. The zanādiqa (heretics) produced entire collections of forged material, but the master critics of hadith exposed their true nature—praise belongs to Allah. A forger may ascribe his own words, or the sayings of certain sages, to the Prophet, and a person may slip into something resembling fabrication without intending to do so. Among the forged reports is the narration attributed to Ubayy ibn Kaʿb that assigns a distinct virtue to each surah of the Quran; every exegete who has cited it has erred. Allah knows best.

Twenty-second Category: al-maqlūb (the inverted report)
This is exemplified by a well-known hadith that originally comes from Sālim but was presented as coming from Nāfiʿ in order to lend it greater appeal. The scholars of Baghdad once inverted one hundred hadiths to test al-Bukhārī; he restored each of them to its proper form, whereupon they acknowledged his superiority. Allah knows best.

Sub-issue
If you encounter a hadith with a weak chain, you may say: “It is weak with this isnād.” Do not say, “Its text is weak,” merely because this particular chain is deficient—unless the one who said