This is the Torah: when a man dies in a tent, all who come into the tent and all that is in the tent shall be unclean seven days.
Torah Temimah: Berachos 43b — Reish Lakish said: From where do we know that the words of Torah are sustained only in one who kills himself over them? As it is said “This is the Torah: a man who dies in a tent.”
English: Reish Lakish said: From where do we know that the words of Torah are sustained only in one who kills himself over them? As it is said “This is the Torah: a man who dies in a tent.”
Homiletic derivation from the juxtaposition of “Torah” and “dies in a tent.”
True acquisition and retention of Torah requires total self-dedication, metaphorically “killing oneself” over it (i.e., extreme effort and self-sacrifice).