Over and over again, Rashi on Chumash points out that a hey at the end of the word means the same as a lamed at the beginning. He doesn't just clarify that that is the usage, he states the rule itself many many times. (In Bereishis alone, 14:10, 15:23, 28:2, 32:4, 33:27, 46:1, and more...)
Why does he restate this rule so much? After the first time, if he just wanted to point out that this is the situation in each case, he could do it in one word e.g.
: מרתה . למרה
Why the repetition?