Gospel (Mk 13,33-37) - At that time, Jesus said to his disciples: «Be careful, keep watch, because you don't know when the time is. He is like a man, who has departed after having left his home and given power to his servants, to each of him his task, and ordered the doorkeeper to keep watch. Watch therefore: you do not know when the master of the house will return, whether in the evening or at midnight or at cockcrow or in the morning; Make sure that when he arrives unexpectedly, he doesn't find you asleep. What I say to you, I say to everyone: keep watch!

The commentary on the Gospel edited by Monsignor Vincenzo Paglia

With the days of Advent the Church wants to prepare us to welcome the Lord who is born among men. We are so focused on ourselves and our things that we risk not noticing Christmas. Not that of the calendar, but that of the heart. Without Christmas we remain as we are, we continue to revolve around ourselves. Let us make Isaiah's prayer our own: «Why, Lord, do you let us wander away from your ways and let our hearts harden, so that we do not fear you? Return for the love of your servants… If only you would rend the heavens and come down!” (Is 63,17.19). And again: «Return for the love of your servants!». We need Christmas. The whole world needs it: the countries crushed by war, the poor, the weak, the children. Refugees, prisoners, the sick, the elderly alone need it. Those who live in the great suburbs of our cities which have become true deserts of love and life need it. It is easy to lose the sense of waiting when you are caught up in your own "I".
The season of Advent makes us raise our eyes high and open our hearts to wait for the Lord: "Be careful, keep watch, for you do not know when the time is" (13.33). Jesus asks us to be like a doorman who keeps watch all night so that the master doesn't come back, knock on the door and the doorman sleeps. Even if it is night - the night of many sad situations in the world -, the doorman must keep watch and open as soon as the master knocks: it can happen in the evening or at midnight or at cockcrow or in the morning. It's a strange, but clear, similarity. It's easy to fall asleep in the sweet warmth of thinking about where you belong because we've already done a lot. Just as it is easy to be surprised by the somewhat sad sleep of pessimism, by that sloth that makes it not worth doing anything, or even by the restless and always dissatisfied sleep of self-affirmation. The Word of God wakes us up. This is why in this time we must listen to it every day. And particularly in the Sunday liturgy.
The Word keeps us awake like the doorkeeper of the Gospel, so that he immediately opens the door - that of the heart but not only - when the Lord knocks: he can be a brother, a sister, a poor person, a stranger, a friend who is in need and who maybe it's even annoying. Every time it is the Lord himself who knocks. The disciple's vigilance, therefore, is not a simple active vigil, but welcoming as a lifestyle.