Catena Aurea on Mark 9:9–13: John Chrysostom

But what Christ answered to this, is seen by what follows, “And He answered and told them, Elias verily cometh first, and restoreth all things;” in which He shews that Elias will come before His second advent. For the Scriptures declare two advents of Christ, namely, one which has taken place, and another which is to come; but the Lord asserts that Elias is the forerunner of the second advent.