“Great is the Torah which endows one who does its teachings with life in this world and the World to Come.” — (Avot 6:7)
“Does its teachings” is used rather than “learns” to remind us that the principal goal of learning is in order to do the mitzvot of G-d’s Torah.
It also communicates the idea that one who learns Torah is considered as if he created that Torah knowledge and it is his own possession. This thought is expressed by King David in the first psalm of Tehillim, when he speaks of it being “G-d’s Torah” before one learns it, and “his own Torah” after he has learned it. “One who does its teaching” then means one who has made those teachings his own creation and possession.
- Midrash Shmuel