Deuteronomy 7:21-24 New International Version (NIV)
21 Do not be terrified by them, for the Lord your God, who is among you, is a great and awesome God. 22 The Lord your God will drive out those nations before you, little by little. You will not be allowed to eliminate them all at once, or the wild animals will multiply around you. 23 But the Lord your God will deliver them over to you, throwing them into great confusion until they are destroyed. 24 He will give their kings into your hand, and you will wipe out their names from under heaven. No one will be able to stand up against you; you will destroy them.
Moses told the Israelites that the enemies of Israel would be destroyed, but this would not happen all at once. Why? God had the power to destroy those nations instantly. He chose to do it in stages. Why? God can instantly and miraculously change your life, but he usually chooses to make change gradually. You are taught lessons one at a time. We as people want change and spiritual maturity all at once. We want solutions to our problems in an instant. God can do this if he chooses, but working one step at a time and trusting God to make up the difference between where you began and where you are going makes more of an impact on your growing relationship with God. The Israelites needed a step by step growing relationship with God, just as we need that for ourselves today. When you look back at your transformation as you grow step by step with God, you will see that miraculous transformation embedded in who you are becoming through Christ Jesus.