Muhammad al-Bukhari
Forgery "took place on a massive scale" which threatened to undermine hadith's divine legitimacy of reports of the Prophet. An idea of how massive the scale was can be gleaned from the fact that Muhammad al-Bukhari, perhaps the most famous collector of hadith, reportedly examined nearly 600,000 narrations, and eliminated all but approximately 7400 (this includes different versions of the same report and repetitions of the same report with different "isnad", i.e. chains of transmitters).