Adam Clarke on Joshua 17:12

Could not drive out, etc. - They had neither grace nor courage to go against their enemies, and chose rather to share their territories with those whom the justice of God had proscribed, than exert themselves to expel them. But some commentators give a different turn to this expression, and translate the passage thus: But the children of Manasseh could not (resolve) to destroy those cities, but the Canaanites consented to dwell in the land. And as they were willing to pay tribute, and the others chose to tolerate them on those terms, they agreed to dwell together: but this paying of tribute seems not to have taken place till some time after, when the children of Israel were waxen strong, etc.