John Calvin Commentary Numbers 33:55

"But if ye will not drive out the inhabitants of the land from before you, then shall those that ye let remain of them be as pricks in your eyes, and as thorns in your sides, and they shall vex you in the land wherein ye dwell." — Numbers 33:55 (ASV)

But if you will not drive out. We have elsewhere seen why God’s wrath was so greatly aroused against those nations that He desired them to be exterminated. Even in Abraham’s time, gross indulgence in sin had begun to prevail there, as we gather from God’s word, when He said that their iniquity was not yet full. After they had abused the forbearance of God Himself for 400 years, who will deny that their destruction was the just and reasonable reward of their long obstinacy?

Still, in cutting them off, God had regard for His elect people, so that they might be separated from the heathen and never turn aside to foreign superstitions. But the Israelites deserved the punishment threatened here twice over due to their remissness, for they failed to perform their duty in executing God’s vengeance and, as far as it was in their power, they detracted from His grace. He had conferred no common honor upon them when He appointed them to be His ministers for executing His judgments. It was therefore shameful inactivity on their part to be remiss on this point.

Furthermore, He had given them the whole land. When, therefore, they contented themselves with part of it and neglected the rest, their perverse ingratitude revealed itself through their indifference. Besides, they had willfully entangled themselves in deadly snares by mixing with heathen nations, from whom God had separated them, so that they would not imitate their habits and corrupt religious ceremonies. God, therefore, threatens that these nations shall be as prickles to pierce their eyes, and thorns in their sides.

That this was fulfilled, the Book of Judges affords the clearest and most ample testimony, although even to the days of David, this punishment was continually inflicted upon their eyes and sides. Thus, also, their untamable stubbornness is proved, since such a solemn admonition had no effect in prompting²²⁷ them to advance, either in the open punishment of iniquity or in a course of victory and success.

²²⁷ “Pour les faire marcher vertueusement parmi leur vietoires, a punir les crimes dont ils estoyent juges;” to cause them to advance virtuously amidst their victories, in punishing the crimes of which they were the judges. — Fr..