William Burkitt on Matthew 24:29

Our Saviour goes on in figurative expressions to set forth the calamities that should befall the Jewish nation, immediately after the destruction of Jerusalem: The sun shall be darkened: that is, all their glory and excellency shall be eclipsed, all their wealth and prosperity shall be laid waste; the whole government, civil and ecclesiastical, destroyed; and such marks of misery found upon them, as never were seen upon a people.

By the sign of the Son of man, the papists will have understood the sign of the cross. Others understand it of those prodigies which were seen a little before the destruction of Jerusalem, which Josephus mentions; as, namely, a comet in the form of a sword hanging over the city for a year together; a light in the temple and about the altar, seen at midnight for half an hour; a cow, led by the priest to be sacrificed, calved a lamb; a voice heard in the temple, saying Abeamus hinc, "Let us go hence."

Learn hence, God premonishes before he punishes; he warns a people of destruction often, before he destroys them once.