A treatise on correcting the letter (dād) by Sajghali Zadeh, who died (1150 AH), investigation and study.

This research is a step in the field of investigation with the aim of reviving the Arabic heritage. The importance of the work stems from the stature of its compiler and the content of the text. Its compiler is Sheikh Al-Marashi, known as Sajgholi Zadeh (d. 1150 AH), one of the leading scholars of Tajweed, and his researched message includes addressing one of the phonetic problems in the Arabic language in general and in the field of Tajweed in particular, which is how to control the pronunciation of the sound of the dd in an eloquent manner, and distinguish it from other sounds close to it, noting that this thesis includes clarification of some of the ambiguities that have been posed to scholars by what was mentioned in his previous letters, so he tried to uncover them with this composition, in addition to the research removing the confusion that occurred. For recent scholars, there is a link between this letter and other letters by the same author that are close to this title. The research also showed the chronological succession of the composition of these letters and their relationship to each other in the arrangement of the ideas through which he intended these works.