Deuteronomy 7:21-23

7:21 You must not tremble in their presence, for the Lord your God, who is present among you, is a great and awesome God. 7:22 He, the God who leads you, will expel the nations little by little. You will not be allowed to destroy them all at once lest the wild animals overrun you. 7:23 The Lord your God will give them over to you; he will throw them into a great panic until they are destroyed.