Albert Barnes Commentary Psalms 78:55

"He drove out the nations also before them, And allotted them for an inheritance by line, And made the tribes of Israel to dwell in their tents." — Psalms 78:55 (ASV)

He cast out the heathen also before them - literally, the nations. The idea of their being pagan, in the sense that is now attached to that word, is not in the original. The word is one that would be applied to any nation, without reference to its religion. These nations were, indeed, pagans according to the present use of that term, but that idea is not necessarily in the Hebrew word.

And divided them an inheritance by line - Divided to his people an inheritance by a measurement of the land. That is, the land was partitioned out among the tribes by a survey, fixing their limits and boundaries. See Joshua 13:7; Joshua 18; Joshua 19.

And made the tribes of Israel to dwell in their tents - To dwell securely and quietly, no longer roaming from place to place, but having a fixed habitation and a home.