But the Lord is faithful, who will establish you, and guard you from the evil one.
Keep -- Paul is fond of military terms, the term to guard, gives the picture of soldiers guarding their commander, or body guards to some official. Used in Luke 2:8, of the shepherd "keeping watch" over their flock by night, and in Acts 12:4 when four quaternions of solder are assigned to guarding Paul, and in Acts 23:35 where Paul is kept in for judgment by Felix. And in many other places.