Rashi on Numbers 26:54/רש"י על במדבר כ״ו:נ״ד

1לרב תרבה נחלתו TO THE NUMEROUS THOU SHALT GIVE MORE INHERITANCE — To the tribe that had a numerous population they gave a large portion of land. Although the portions were not of equal area because, as we have now said, in all cases they assigned the portions according to the size of the tribe, yet they did so only by aid of the lot, but the lot fell by the utterance of the Holy Spirit, as is explained in Baba Batra 122a: Eleazar the Priest was clothed with the Urim and Thummim, and spake by the Holy Spirit, “If such-and-such a tribe comes up, such-and-such a territory shall come up with him”. The names of the tribes were written on twelve tablets, and those of twelve districts on twelve tablets. They mixed them in an urn, and the prince of a tribe inserted his hand in it and took out two tablets. There came up in his hand the tablet bearing the name of his tribe and the tablet relating to the district that had been declared by the Urim and Tummim to be intended for it. The lot, itself cried out, saying, “I, the lot, have come up for such-and-such a district for such-and-such a tribe”, as it is said, (v. 56) על פי הגורל by the mouth (utterance) of the lot [shall the possession thereof be divided]” (Midrash Tanchuma, Pinchas 6). The land was not divided by measurement alone because one district is superior to another but it was divided by estimating its fertility: a bad piece of land sufficient to sow a Kor was regarded as the equivalent of a good piece of land sufficient to sow a Seah (the thirtieth part of a Kor) — all depended upon the value of the soil.