In this the children of God and the children of the devil are manifest: Whoever does not practice righteousness is not of God, nor is he who does not love his brother. 1 John 3:10
To be manifest is to be made apparent or seen clearly.
There is going to be a change in those who give themselves to Jesus. John here points out that the touch of God is going to show in the behavior of the saved. While the world wants all to come together as one people, there is a division going on perpetrated by the very Word of God. The division that takes place internally in Hebrews 4:12, also is made manifest in the world as a population. We don't get to have the old flesh of sin show up in Heaven with the new spirit of righteousness.
Some would say that churches must include everyone in order to show brotherly love. However, the Word speaks in the Revelation of people who do not belong in His churches. There are those who are the children of the devil made manifest who also want to come into the church without repentance. It is like the Bride of Christ is putting on the robe of His righteousness while the enemy is handing her the filthiest of rags and demanding that she wear these too. And then the big lie is spoken, "See how judgmental this Church is? She must include all or she does not love as she ought." Sorry, but the Bride of Christ cannot be any less than perfectly prepared to wed God's Son. And for that we must be separated from the sins of this world.
Those saved by the blood of the Lamb earnestly desire our purity; and though we are not there yet, a manifest separation is taking place each and every day. The most obvious time will be that of the Rapture when one will be taken and the other left behind. Now that is a manifestation!Grace and peace to you who belong to the Son!