From the early Church Fathers to now.
“For it was the sentence of the Lord, that their hearts should be hardened, and they should fight against Israel, and fall, and should not deserve any clemency, and should be destroyed as the Lord had commanded Moses.”
“For as long as the hostile powers that work sin in us do not come and incite us to sin or provoke us to fight, they cannot be killed or exterminated. For that reason, therefore, God is said in like manner to permit, even to excite, opposing powers to go out into battle against us so that we may seize the victory and they may pursue destruction.”
“"There was no city which the Lord did not deliver to the children of Israel, except perhaps those who lived in Gibeon. Israel violently overthrew all of them because the Lord hardened their hearts that they would fight Israel and be killed and not be shown mercy and die, just as the Lord had commanded Moses." If it happened by the will of the Lord that Israel not receive or accept peace, then let us say with the apostle, "Why, therefore, does he object? For who can resist the will of the Lord?"”
“It is said that "their heart was strengthened through the Lord," that is, that their heart was hardened, just as in the case of Pharaoh. There can be no doubt that this is justly done by a divine and lofty judgment, when God abandons someone and the enemy takes possession of him; the same applies in this case as in Pharaoh's. But here something else sets in motion, as it is said that their hearts were emboldened to arise against Israel in war and therefore the Israelites would not show any mercy to them. The Israelites may very well have showed them mercy, if the Canaanites had not gone to war, since God had ordered that none of the Canaanites were to be spared and yet the Israelites had spared the Gibeonites because they had represented themselves as having come from a far-off country and had made a treaty with them. But because the Israelites showed mercy to some, albeit against the command of God, it must be understood that it was said with this intention that the Canaanites waged war in such a manner so that the Israelites would not spare them, nor would the Canaanites be able to convince the Israelites to show mercy and neglect God's command. I cannot believe that this could have happened in any other way, even though Joshua was their leader and diligently obeyed all of God's commands. Nonetheless, not even Joshua would have annihilated them so quickly had they not gone against him in such a dastardly fashion. Thus it could have happened that Joshua, taking care to fulfill God's commandments, would have defeated them in a rather minimal way and they would have remained until the time when the Israelites could spare them after Joshua's death, when the Israelites did not do God's commandments with such care. For even while he was still alive the Israelites spared some Canaanites, although they subjugated them to their authority; some Canaanites, in fact, they never could conquer. But these things were not done while he was their leader but when as an old man he had retired from warfare and merely divided up the territories for the Israelites. He divided it with the intention that the Israelites would take possession of those lands that were emptied of the enemy and capture the rest by fighting, although he himself would no longer wage war. And the fact that they were able to conquer some of the Canaanites in a rather minimal way was owing to divine providence, as is clear in certain places in the Scriptures.”
The in-app commentary runs from the Fathers to the early-modern record, then stops — that's where the public-domain sources end, not where the reading does. For the modern reading, follow the sources directly.