They shall be snares - לפח lephach, a net or gin, set by the artful fowler to catch heedless birds.
And traps - מוקש mokesh, any snare, toil, or trap, placed on the ground to catch the unwary traveler or wild beast by the foot.
Scourges in your sides, and thorns in your eyes - Nothing can be conceived more vexatious and distressing than a continual goad in the side, or thorn in the eye. They will drive you into obedience to their false gods, and put out the eyes of your understandings by their idolatries. And God will preserve them merely to distress and punish you.

Know for a certainty that the Lord your God will no more drive out any of these nations from before you,.... Or, "knowing ye shall know" (r); or "know ye"; this may be taken for granted, or the fullest proof, and clearest demonstration, and strongest assurance will be given of it, that in case of such bad conduct, and disobedience to the will of God, no more of the nations of the Canaanites will be driven out of the cities in which they are:

but they shall be snares and traps unto you; who by their bad examples would draw them both to idolatry and superstitious worship, and into all irreligion, profaneness, and immorality, as they did, Psa 106:35,

and scourges in your sides; who either, by ensnaring them, would get an advantage over them, and distress them in their persons, families, and estates; or would be the means of the Lord's correcting and chastising them with the rod and stripes of men, for the iniquities these would draw them into; the allusion is to scourges and lashes laid on the sides of men, or to goads with which beasts are pushed on their sides and driven:

and thorns in your eyes; very troublesome and distressing; for even a mote in the eye is very afflicting: and much more a thorn; See Gill on Num 33:55. Jarchi interprets this word by camps surrounding them, as shields do the bodies of men, and which is approved of by Gussetius (s):

until ye perish from off this good land, which the Lord your God hath given you; by sword, famine, pestilence, or captivity, which has been their case.

(r) "sciendo scietis", Montanus; "sciendo scitote", Pagninus, Vatablus. (s) Comment. Ebr. p. 717.

BY THREATENINGS IN CASE OF DISOBEDIENCE. (Jos 23:12)

Else if ye do in any wise go back, and cleave unto the remnant of these nations--As marriage connections with the idolatrous Canaanites would present many and strong temptations to transgress it, these were strictly prohibited (Exo 34:12-16; Deu 7:3). With his eye, as it were, upon those prohibitions, Joshua threatens them with the certain withdrawal of the divine aid in the further expulsion of the Canaanites (a threat founded Exo 23:33; Num 33:55; Deu 7:16).

Next: Joshua Chapter 24