Theophylact of Ohrid — as excerpted in the Catena Aurea on Luke 21:28-33

“For because He had foretold that there should be commotions, and wars, and changes, both of the elements and in other things, lest any one might suspect that Christianity itself also would perish, He adds, Heaven and earth shall pass away, but my words shall not pass away: as if He said, Though all things should be shaken, yet shall my faith fail not. Whereby He implies that He sets the Church before the whole creation. The creation shall suffer change, but the Church of the faithful and the words of the Gospel shall abide for ever.”