Gregory the Great
Catena Aurea · Lukasevangelium 21
And when these things begin to come to pass, then look up, and lift up your heads; for your redemption draweth nigh. And he spake to them a parable; Behold the fig tree, and all the trees; When they now shoot forth, ye see and know of your own selves that summer is now nigh at hand. So likewise ye, when ye see these things come to pass, know ye that the kingdom of God is nigh at hand. Verily I say unto you, This generation shall not pass away, till all be fulfilled. Heaven and earth shall pass away: but my words shall not pass away.
(ut sup.) Or else, The heaven and earth shall pass away, &c. As if He says, All that with us seems lasting, does not abide to eternity without change, and all that with Me seems to pass away is held fixed and immoveable, for My word which passeth away utters sentences which remain unchangeable, and abide for ever.