Rashi on Numbers 33:54/רש"י על במדבר ל״ג:נ״ד

1אל אשר יצא לו שמה — This is an elliptical verse, the meaning being, the place where the lot falleth to anyone, that shall be his.

2למטות אבותיכם ACCORDING TO THE TRIBES OF YOUR FATHERS [YE SHALL DIVIDE INHERITANCE] — i.e., according to the number of those who came out of Egypt (Bava Batra 117a; cf. Rashi on Numbers 26:55). Another explanation: ye shall divide it into twelve districts, as is the number of the tribes.