John Calvin's Bible Commentary
Joshua 21:43
43.And the Lord gave unto Israel, etc Should any one raise a question as to this rest, the answer is easy. The nations of Canaan were so completely overcome with fear, that they thought they could not better consult their interest than by servility flattering the Israelites, and purchasing peace from them on any terms. (176) Plainly, therefore, the country was subdued and rendered peaceful for habitation, since no one gave any annoyance, or dared to entertain any hostile intentions, since there were no threats, no snares, no violence, no conspiracies.
A second point, however, raises some doubt, (177) namely, how the children of Israel can be said to have been settled in the possession of the land promised to them, and to have become masters of it, in such a sense that in regard to the enjoyment of it, not one syllable of the promises of God had failed. For we have already seen that many of the enemy were intermingled with them. The divine intention was, that not one of the enemy should be permitted to remain; on the other hand, the Israelites do not drive out many, but admit them as neighbors, as if the inheritance had been common to them; they even make pactions with them. How then can these two things be reconciled, that God, as he had promised, gave possession of the land to the people, and yet they were excluded from some portion by the power or obstinate resistance of the enemy?
In order to remove this appearance of contradiction, it is necessary to distinguish between the certain, clear, and steadfast faithfulness of God in keeping his promises, and between the effeminacy and sluggishness of the people, in consequence of which the benefit of the divine goodness in a manner slipped through their hands. Whatever war the people undertook, in whatever direction they moved their standards, victory was prepared; nor was there any other delay or obstacle to their exterminating all their enemies than their own voluntary torpor. Wherefore, although they did not rout them all so as to make their possession clear, yet the truth of God came visibly forth, and was realized, inasmuch as they might have obtained what was remaining without any difficulty, had they been pleased to avail themselves of the victories offered to them. The whole comes to this, that it was owing entirely to their own cowardice that they did not enjoy the divine goodness in all its fullness and integrity. This will be still clearer from the following chapter.