Tanya Chapter 37 part 6

So much of your vital soul, and often its totality, is invested in earning a livelihood. Thus, when hard-earned money is given to charity, this one act brings the entire vital soul up to Hashem. That is why the Sages of the Land of Israel called charity simply “the mitzvah.” Because it embodies what a mitzvah is all about and is outstanding in this respect –– elevating the vital soul to holiness. So why did the Sages say that “Torah study outweighs them all?” Because there is something unique to Torah study, influencing and transforming the vital soul in a way that no other mitzvah can.