‘From what does God call men?
(1.) From sin. He calls them from their ignorance and unbelief. 1 Pet 1:14. By nature the understanding is enveloped with darkness. God calls men ‘from darkness to light,’ as if one should be called out of a dungeon to behold the light of the sun. Eph 5:8.
(2.) From danger. As the angels called Lot out of Sodom, when it was ready to rain fire; so God calls his people from the fire and brimstone of hell, and from all those curses to which they were exposed.
(3.) He calls them out of the world; as Christ called Matthew from the receipt of custom. ‘They are not of the world.’ Jn 17:16. Such as are divinely called, are not natives here, but pilgrims; they do not conform to the world, or follow its sinful fashions; they are not of the world; though they live here, yet they trade in the heavenly country. The world is a place where Satan’s throne is. Rev 2:12. It is a stage on which sin every day acts its part. Now such as are called are in the world but not of it.’
(Thomas Watson, A Body of Divinity)