The research reviews Arabic dialects in Taysir Al-Tafsir (lit. Facilitation of Interpretation) by Sheikh Muhammad bin Yousef Tfayyesh. The candidate collects the dialects mentioned in Sheikh Tfayyesh's book, and then studies every problem according to the study plan. The candidate indicates the Arab tribes that used each dialect and the integrity of Sheikh Tfayyesh's statements along with some points Sheikh Tfayyesh did not mention based on citations of relevant Qur'anic verses, lines of poetry, or narrations to reach the most likely conclusions. The candidate relies on both sama' (narrations) and qiyas (deductive analogy) while pointing to the most eloquent or standard thereof. The candidate has also renders some dialectical texts in their relevant modern dialects especially that of the people of Oman and Semitic languages based on translated sources and modern dialectical studies. The study consists of a preface, four chapters and a conclusion in which the candidate states the most important findings. The preface introduces the biography of Sheikh Muhammad bin Yousef Tfayyesh, defines "language" and "dialect" and overviews Sheikh Tfayyesh's approach in his study of dialects. Chapter One address the phonetic issues of hamz (glottalization) and ibdal (replacement or mutation). Chapter Two touches upon the morphological issues, such as the morphological scale, structure of infinitives, masculine and feminine, and I'lal (vowel changes) Chapter Three deals with the grammatical issues, such as nouns, verbs, words that can be nouns or verbs, and letters. Chapter Four handles the lexicological dialectical issues and their entries as per alphabetical order. The study concludes with the findings the candidate reaches.