We cannot come to God unless God calls us to come. And it is not until God enlivens our hearts with faith in Jesus Christ, the Son of God, that we are called.
The Moabites and the Ammonites could not come. They were the children of an ancient incestuous act (Genesis 19:30-38). But perhaps more importantly, they had rejected God and his people, denying them even basic support in the wilderness and hiring a sorcerer to curse them.
The Moabites and the Ammonites were not Israelites in a physical sense. Nor were they in a spiritual sense.
But God always has made a way for people to come, even if they were barred physically. Even a Moabite could come to God in faith (Ruth 1:16). And remarkable things sometimes happened when they did (Matthew 1:5-6, 16).
We are reminded in Deuteronomy 23 of the supreme impossibility of coming into God’s presence without a heart laden with faith in Him. We are a fragile people marked by too many mistakes and impurities.
But faith causes us to look at the barriers between us and God, and to ask for a way through. When we do that out of the deepest desire of our hearts, we know God is calling us to himself. “For the promise is for you and for your children and for all who are far off, everyone whom the Lord our God calls to himself” (Acts 2:39).