Joshua 18:4

Give out from among you three men for each tribe: and I will send them, and they shall rise, and go through the land, and describe it according to the inheritance of them; and they shall come again to me.

Give out from among you three men for each tribe. Though the lot determined the part of the country where each tribe was to be located, it could not determine the extent of territory which might be required; and the dissatisfaction of the children of Joseph with the alleged smallness of their possession gave reason to fear that complaints might arise from other quarters, unless precautions were taken to make a proper distribution of the land. For this purpose a commission was given to 21 persons-three chosen from each of the seven tribes which had not yet received their inheritance-to make an accurate survey of the country. They "went and passed through the land, and described it by cities into seven parts in a book" (Joshua 18:9); dividing the land according to its value, and the worth of the cities which it contained, into seven equal portions.

This was no light task to undertake. It required learning and intelligence, which they or their instructors had, in all probability, brought with them out of Egypt. Accordingly, Josephus ('Antiquities,' b. 5:, ch. 1:, sec. 21) says that the survey was performed by men expert in geometry. And, in fact, the circumstantial account which is given of the boundaries of each tribe and its situation well proves it to have been the work of no mean or incompetent hands.