Exodus 23:28-30

I will send something like hornets ahead of you. They will force the Hivites, Canaanites and Hittites out of your way. But I will not force all those people out in only one year. If I did, the land would become a desert. Then the wild animals would become too many for you. Instead, I will force those people out of your land very slowly. I will wait until there are enough of you to take over the land.