Augustine of Hippo — as excerpted in the Catena Aurea on Mark 13:21-27

“(de Trin. i. 13) For the vision of the Son of Man is shewn even to the bad, but the vision of the form of God to the pure in heart alone, for they shall see God. (Matt. 5:8) And because the wicked cannot see the Son of God, as He is in the form of God, equal to the Father, and at the same time both just and wicked are to see Him as Judge of the quick and dead, before Whom they shall be judged, it was necessary that the Son of Man should receive power to judge. Concerning the execution of which power, there is immediately added, And then shall he send his angels.”