This paper scrutinizes the relationship between Arabic grammar and tafsīr “Qurʾānic exegesis” through investigating the phenomenon of iʿrāb al-jumal “the analysis of sentences’ syntactic functions.” Whereas iʿrāb analyzes words’ syntenic relations within one sentence, iʿrāb al-jumal examines the syntactic status of a sentence within an utterance(s). This study argues that grammar plays a significant role in tafsīr. It investigates iʿrāb al-jumal in two medieval works: Ibn Hishām’s Mughnī al-Labīb in grammar and al-Zamakhsharī’s al-Kashshāf in tafsīr to illustrate the importance of grammar in tafsīr. The paper consists of three chapters. The first chapter reviews different approaches in Qurʾānic interpretation, focusing on the development of the linguistic approach. The second chapter investigates the theorization of iʿrāb al-jumal in Mughnī al-Labīb, which was the first work to study the syntactic functions of sentences comprehensively. The third chapter analyzes examples of the employment of iʿrāb al-jumal to justify Qurʾānic interpretations in al-Kashshāf.