Origen

Or, we need not understand this of a local gathering together, but that the nations shall be no more dispersed in divers and false dogmas concerning Him. For Christ’s divinity shall be manifested so that not even sinners shall any longer be ignorant of Him. He shall not then shew Himself as Son of God in one place and not in another; as He sought to express to us by the comparison of the lightning. So as long as the wicked know neither themselves nor Christ, or the righteous see through a glass darkly, (1 Cor. 13:12.) so long the good are not severed from the evil, but when by the manifestation of the Son of God all shall come to the knowledge of Him, then shall the Saviour sever the good from the evil; for then shall sinners see their sins, and the righteous shall see clearly to what end the seeds of righteousness in them have led. They that are saved are called sheep by reason of that mildness which they have learnt of Him who said, Learn of me, for I am meek and lowly, (Mat. 11:29.) and because they are ready to go even to death in imitation of Christ, who was led as a sheep to the slaughter. (Isa. 53:7.) The wicked, are called goats, because they climb rough and rugged rocks, and walk in dangerous places.