Dominica Prima Adventus: "And there shall be signs in the sun, and in the moon, and in the stars"

From the Holy Gospel according to Luke
Luke 21:25-33
In that time, Jesus said to his disciples: And there shall be signs in the sun, and in the moon, and in the stars; and upon the earth distress of nations. And so on.

Homily by Pope St. Gregory the Great,
1st on the Gospels.
Our Lord and Saviour wisheth to find us ready at His second coming. Therefore He telleth us what will be the evils of the world as it groweth old, that He may wean our hearts from worldly affections. Here we read what great convulsions will go before the end, that, if we will not fear God in our prosperity, we may at least be scourged into fearing His judgment when it is at hand.