The Apostle recalls this separation, saying: "The firm foundation of God stands, and the Lord knows His own," and, "Let everyone who confesses the name of the Lord depart from unrighteousness" (2 Tim 2:19).
"Lest you take part," says John, "in her sins, and lest you receive her plagues." Since it is written, "The righteous man, though he die early, will be at rest" (Wis 4:7), how can the righteous share in the sin which the city's fall destroyed with the impious?
Only in this way: when the righteous leave the city of the devil, that is, luxurious and impious life. If one of them wished to remain and surrender to the lusts of Babylon, he would undoubtedly share in its sins.
When Scripture often says, "Come out," do not understand it in a bodily sense, but spiritually. To come out of Babylon means to renounce an evil way of life.
For in one house, in one church, and in one city, Babylon and Jerusalem exist together. Yet as long as the righteous do not consent to the evil, and the evil are not changed into the righteous, Jerusalem is recognized in the righteous and Babylon in the evil.
They live together in the body, but they are greatly separated in heart. The life of evil men is always on the earth, because they love the earth and set all their hope and desire of soul upon the earth.
But the mind of the righteous, according to the Apostle, is always in heaven, for they set their mind on things above (cf. Col 3:2).