John Gill Commentary Joshua 21

Then came near the heads of the fathers of the Levites When the land was divided to the several tribes, and everyone knew the cities that belonged to them, and what they could and should part with to the Levites, and when the six cities of refuge were fixed; the Levites came to put in their claim for cities of habitation, they having no share in the division of the land; and yet it was necessary they should have habitations; the persons that undertook to put in a claim for them were the principal men among them; the fathers of them were Kohath, Gershon, and Merari; the heads of those were the chief men that were then living: these came

unto Eleazar the priest, and unto Joshua the son of Nun ; the high priest and chief magistrate:

and unto the heads of the fathers of the tribes of the children of Israel ; the princes appointed to divide the land with the two great personages before mentioned, (Numbers 34:17–29) .

And they spake unto them at Shiloh in the land of Canaan
Where the tabernacle was fixed, at or near which the above persons met to cast lots for the division of the land to the seven tribes that had not received their inheritance:

saying, the Lord commanded by the hand of Moses to give us cities to
dwell in, with the suburbs thereof for our cattle ;
this command is extant in (Numbers 35:2–8) .

And the children of Israel gave unto the Levites out of their
inheritance
Knowing full well there was such a command, made no objection to their motion, but freely gave them cities out of the portion of inheritance allotted to them; this they did

at the commandment of the Lord, and in obedience to it, even gave
these cities and suburbs ;
after mentioned: this was done by the tribes themselves; as there were a certain number fixed by the commandment of God, they agreed among themselves how many and what cities should be given out of each tribe; and then lots were cast for them by Joshua, what and which cities should be appropriated to their several divisions, as the Kohathites that sprang from Aaron, and the rest of them that did not, and the Gershonites and Merarites, as follows.

And the lot came out for the family of the Kohathites
The first lot that was drawn out of the pot or urn was for the descendants of Kohath, a son of Levi:

and the children of Aaron the priest, [which were] of the Levites ;
who descended from Amram, the eldest son of Kohath, and these were not only Levites, but priests: these

had by lot out of the tribe of Judah, and out of the tribe of Simeon ,
and out of the tribe of Benjamin, thirteen cities ;
which are after mentioned by name; and as these were priests, whose business was to serve in the temple, and at the altar, the cities assigned them by the lot, were, by the wise disposal of divine Providence, ordered them out of those tribes which lay nearest to Jerusalem; the place God had chosen to put his name in, where the temple would be built, and the altars erected for sacrifices and incense.

And the rest of the children of Kohath Which did not descend from him in the line of Amram and Aaron, but of Izhar, Hebron, and Uzziel, who were not priests, but Levites:

[had] by lot out of the families of the tribe of Ephraim, and out of the tribe of Dan, and out of the half tribe of Manasseh, ten cities ; these other sort of Kohathites had their cities in tribes next to the other three where the Kohathites that were priests had theirs.