Bede the Venerable
Catena Aurea · Markusevangelium 13
Now learn a parable of the fig tree; When her branch is yet tender, and putteth forth leaves, ye know that summer is near: So ye in like manner, when ye shall see these things come to pass, know that it is nigh, even at the doors. Verily I say unto you, that this generation shall not pass, till all these things be done. Heaven and earth shall pass away: but my words shall not pass away.
(ubi sup.) The heaven which shall pass away is not the ethereal or starry heaven, but the heaven where is the air. For wheresoever the water of the judgment could reach, there also, according to the words of the blessed Peter, the fire of judgment shall reach. (2 Pet. 3) But the heaven and the earth shall pass away in that form which they now have, but in their essence they shall last without end.