Bible Notes Online - Joshua 18 - ESV
Commentary

v3: Although seven tribes still had not occupied their possessions (v1-2), Joshua insisted that the problem was their neglect (compare Heb 2.3). Sometimes we miss out on God’s blessings because we fail to avail ourselves of them.

v4-5: Joshua directed that three men from each of the tribes were to survey the land, in the northern part of Canaan, and divide it into seven parts. The allotment to each tribe was then to be decided by casting lots (v6).

v7: The inheritance of the Levites; see 13.14, 35.

v8-10: Joshua’s wisdom, in sending three men from each tribe. The description they produced would have their implicit agreement, and therefore avoid future disputes over territory.

v11: Benjamin's lot was between Judah and Joseph, a place of safety, The description of the northern border in v12-13 matches that of Joseph in 16.1-2; the description of the southern border in v15-19 matches that of Judah in 15.5-9.

v16: The valley of Ben Hinnom was later a place of idolatry; Jer 7.13,19; 2 Chr 33.6. This was close to Jerusalem, the centre of true religion; idolatry had even reached the heart of Israel.

Here Jerusalem is referred to as the Jebusite city, indicating that the inhabitants had yet to be defeated.