The phrase, “I will be their God and they will be my people” is a familiar phrase. We read it here in Ezekiel as an analogy for how God will unify both Israel and Judah. They have been scattered because of sin but God has not forgotten His covenant with them. It’s interesting to consider what this phrase means for us as Christians today.
We read this same phrase in 2 Corinthians.
Do not be bound together with unbelievers; for what partnership have righteousness and lawlessness, or what fellowship has light with darkness? 15 Or what harmony has Christ with Belial, or what has a believer in common with an unbeliever? 16 Or what agreement has the temple of God with idols? For we are the temple of the living God; just as God said, “I WILL DWELL IN THEM AND WALK AMONG THEM; AND I WILL BE THEIR GOD, AND THEY SHALL BE MY PEOPLE.
2 Corinthians 6:14-16 NASB
The Corinthians had the same problems that Israel and Judah had. They intermingled with foreign idols which caused them to compromise on holiness. When you read both in context, you realize that God’s intention for us under both covenants was to make us holy as He is holy. He says this very clearly in Scripture (1 Pet 1:16).
In both instances, God was the initiator of peace and unification. He went the extra mile to bring Israel and Judah out of captivity and provide new opportunities. He went even further by sending His Son for us as a ransom for sin. Therefore, for those who respond, we will be His people and He will be our God.