It was so, that when Joshua had spoken to the people, the seven priests bearing the seven trumpets of rams' horns before Yahweh passed on, and blew the trumpets: and the ark of the covenant of Yahweh followed them.
One result of moral filth is physical disease. Therefore, the destruction of the Canaanites (in some cases together with their sheep and cattle) ensured the removal of deadly diseases that could have threatened Israel’s existence. The absence of Canaanite religious practices would also be a help to Israel’s religious life and moral well-being.