‘For the children of Joseph were two tribes, Manasseh and Ephraim, and they gave no portion to the Levites in the land, except for cities to dwell in with their suburbs, for their cattle and for their substance.'
With the separation of Levi to the service of YHWH the twelve tribes had been maintained by the split of Joseph into Ephraim and Manasseh to ‘take over' Levi's portion. Thus the land would be fully occupied while Levi could be freed for their service. This demonstrates how important the ‘twelveness' was seen to be. Twelve appears to have been a recognised number of covenant relationship which had to be maintained, compare Genesis 22:20-24; Genesis 25:13-16. Yet it was not said of Manasseh ‘this is the inheritance of the children of Manasseh' although that is said of all the other tribes. They were still not seen as fully separate from Ephraim. This is an indication of the early date of the sources. They would not have thought that way later.
The portion of Levi has previously been described as ‘the offerings of YHWH, the God of Israel, made by fire' (Joshua 13:14) and ‘YHWH, the God of Israel' (Joshua 13:33). Thus it represented participation in supernatural things and special closeness to and separation to YHWH Himself. Now they were to be provided with the means of sustenance, but only as ‘sojourners' in the land. The Levites were regularly described as sojourners (e.g. Deuteronomy 18:6; Judges 17:7-9; Judges 19:1), those who dwell in but have no permanent rights in the land. This in their case was not because they were second class, but because they were super-class. In Leviticus 25:23 a similar concept was applied to all Israel demonstrating that the land belonged to YHWH and could not be sold in perpetuity but should be returned to its former owners at the year of yubile if not before.
“Cities to dwell in with their suburbs, for their cattle and for their substance.” The ‘suburbs' were the common land round a city which were shared by all. Cities were to be set aside in the portions of all the tribes for the Levites to dwell in so that they could carry out their responsibilities to YHWH. This included the collection of tithes, watching over the covenant and the giving of guidance on matters to do with the sanctuary and the Law.