VATICAN CITY (CNS) -- The Annunciation -- the Angel Gabriel announcing to Mary that she will bear God's son -- was such a tremendous, history-changing event that preaching about it is extremely difficult, Pope Francis said.

So, when the Gospel reading for daily Mass Dec. 20 was St. Luke's version of the Annunciation, the pope basically devoted his homily to reading the passage out again.

First, though, he told the small congregation in the chapel of the Domus Sanctae Marthae that the Annunciation is "the decisive moment in history, the most revolutionary."

When Jesus becomes human "everything changes, history turns upside down," he said. "God lowers himself, God enters history and does so in his original style: a surprise. The God of surprises surprises us."

The meaning and message of Christmas was on Pope Francis' mind later in the day when he met 65 young people from the children and young teens section of Italy's Catholic Action.

He asked the young people to share the Christmas message with their peers. "And what is this message? That we are all loved by the Lord. This is the true, great, good news that God gave the world with the coming of his son Jesus among us."

"He loves us! Each and every one of us," the pope said. "This is beautiful."

Praying that his young guests would let Jesus be born in their hearts, Pope Francis encouraged them also to "offer this joy to other youngsters who are living in situations of suffering or going through difficult times, especially those you notice are most alone or are being mistreated."

"Be generous channels of goodness and welcome to build a world that is marked by more brotherhood, more solidarity and is more Christian," the pope told them.