Rashi on the Former Prophets

You have seen how I have alloted to you. By means of the lot for your inheritance.
The remainder of these nations— that remain to be conquered.

And a goad in your sides. They will prowl around you to loot and ransack.
And thorns. This is an expression of camps. Similarly: “And they will come upon you with camps,” like a shield (צִנָה) that surrounds a person on three sides, as it is said, “As a shield, you encompass him with favor,” תַּעְטְרֶנוּ meaning תְּסוֹבְבֶנוּ, surrounding, similar to “And Shaul and his men surrounded David and his men.” עוֹטְרִים meaning סוֹבְבִים, surrounding.