What will cause the population explosion in the millennial kingdom?
According to the context, the great population explosion in the millennial kingdom will come from the early citizens or inhabitants of the kingdom age. Only believers enter that kingdom, and no unbelievers will be in the millennial reign. From those early believing inhabitants, the great population explosion will come.
Les explains that only believers can go into the kingdom, and there will be no unbelievers in the millennial reign. He notes that future lessons will cover who will comprise the early citizens or inhabitants of the kingdom age. From those early inhabitants, he says, will come that great population explosion. For now, he emphasizes that Christ will not only smite the nations but will rule them with a rod of iron as King of kings and Lord of lords.