Tanya begins by stressing importance of Torah study

 He is certainly not one whose deeds are half virtuous and half sinful; for if this were so, how could Rabbah err in [classifying] himself as a Beinoni?

ונודע דלא פסיק פומיה מגירסא, עד שאפילו מלאך המות לא היה יכול לשלוט בו

— when it is known that his mouth never ceased studying [the Torah], so much so that even the Angel of Death had no dominion over him.13