John 17:15

15. Not… take… out of the world Peter was ready (John 13:37) to follow his Lord out of the world. Wearied Christians often would sigh to depart and be with Christ. But that aspiration must be checked within the most reverent limits. What could the world’s great carcass do if the salt should all depart? What but suffer the fate of Sodom for want of ten righteous men? The good men hated by the world are the world’s preservers.

Keep them from the evil For how easy is it for them to assimilate by gentle shadings with the world. The world, then, will no longer hate, however much they will despise them for the compromise. God keeps them, not merely for themselves, but for the honour of his own name, and from mercy to the world that hates them.