And the Lord your God will drive out those nations before you little by little; you will be unable to destroy them at once, lest the beasts of the field become too numerous for you.
Deuteronomy 7:22
When God led His people into the Promised Land, He did so step by step. If He had allowed them to annihilate their enemies at once, the land would have been too difficult to manage. So He allowed some of the enemies to remain for a time in order to maintain the land and suppress the wildlife. In doing so, God taught His people to trust Him step by step. He gave them only as much responsibility as they could handle at one time. As God leads you in your Christian growth, He will allow challenges that match your character and relationship to Him.

