Chapter 21 lists 42 cities situated throughout Canaan, in no centralized area, that were assigned to the Levites, including the priests who were descendants of Aaron who was a Levite. The rabbis later added the six cities identified as cities of refuge to the 42 yielding a total of 48 Levitical cities and 48 places where unintentional murderers could flee to escape blood avengers.
Chapter 21 ends the second part of Joshua. The first part dealt with the conquest and the second with the distribution of Canaanite land.
Chapter 21 contains quite a few problems, including the following:
Numbers 35:4 asserts that the Levite cities should be surrounded by fields of “a thousand cubits round about,” but verse 5 has the measurement of two thousand cubits. The thirteenth century Spanish sage Nachmanides suggested that the extra thousand in verse 5 is land used for cattle. Yet this is not explicit in the text.
Why were the priests placed in the territory of Judah and Benjamin and not dispersed throughout Canaan as were the Levites? Sefer Yehoshua suggests the priests were placed near the Jerusalem temple in which they would serve after King David conquered the city. This is an anachronism since no one knew during the days of Joshua that a temple would exist in Jerusalem. The tabernacle was situated in Shiloh for centuries before David conquered Jerusalem. This is arguably another indication that the book Joshua was composed after the temple was built in Jerusalem; unless we say that the placement of the priests was done by prophecy.
According to verse 8, the Levite cities were assigned by lottery, but in Numbers 35:8 they were allotted by the size of the group.
While chapter 14 indicates Caleb acquired Hebron, 21:11 and 12 report the city was given to the Levites.
The list of Levite cities in Joshua 21 differs with the list in I Chronicles 6.
The four Levite cities in the territory of the tribe of Reuben are missing in the catalogue of cities in Joshua 21, apparently because of a scribal error, but they are mentioned in the Greek Septuagint translation of this chapter.
Generally, each of the twelve tribes relinquished four cities to the Levites, yielding 48, 4 times 12. However, without an explanation, Naphtali only surrendered three, which was rectified by Judah and Simeon giving a total of nine.
Chapter 21 ends saying Israel’s enemies were dispatched and all of Canaan was occupied and settled. Chapter 13:1-6 reports that this was not true, as does the book of Judges, Samuel, and Kings. Arguably, the passage is stating that God arranged that all of Israel’s enemies would be dispatched on the condition that the Israelites obey the divine laws. Judges 2:16-3:6 explain: God allowed some Canaanites to remain “as a means of testing Israel.”
 Some rabbis suggest the Levites were distributed throughout Canaan to teach the Israelites as indicated in Deuteronomy 17:9, and some scholars suggest they were distributed during the kingdoms of King David and King Solomon because they were assigned administrative functions in the various localities (Olam Hatanakh).
 Discussed in chapter 20.
 Mossad HaRav Kook.
 The two are listed together because as we saw in a prior chapter Simeon received no territory of its own, only cities in the Judah allotment.