Sharh 'Illal at-Tirmidhi written by Ibn Rajab al-Hanbali is an Explanation that deals with the science of al-'Illal. This is the science of declaring certain Ahaadith as Da'eef (Weak). This book is a study on the Manhaj of al-Imaam at-Tirmidhi in his arrival to the conclusion that certain Ahaadith are weak. Printed by Maktabtur Rushd on yellow paper in 2 volumes.