Story highlights Benedict deplores the "superficial glitter of this season"

A nativity scene is unveiled in St. Peter's Square

The pontiff will deliver his annual Christmas message Sunday

Pope Benedict XVI presided over Midnight Mass on Christmas Eve, delivering a homily that focused on the "essence" of the holiday rather than the "commercial celebration" it has become.

"Today Christmas has become a commercial celebration, whose bright lights hide the mystery of God's humility, which in turn calls us to humility and simplicity," the pope said after recalling the story of Christmas. "Let us ask the Lord to help us see through the superficial glitter of this season, and to discover behind it the child in the stable in Bethlehem, so as to find true joy and true light."

The 84-year-old pope, presiding over his seventh mass as pontiff, also conjured up an image of the Church of the Nativity in Bethlehem, explaining that visitors must bend down to enter its low opening, drawing a tie to what followers of Christ must do to find their faith.

"If we want to find the God who appeared as a child, then we must dismount from the high horse of our 'enlightened' reason," he said. "... In this spirit let us celebrate the liturgy of the holy night, let us strip away our fixation on what is material, on what can be measured and grasped."

The pope started off Saturday's celebrations by lighting a peace candle in the window of his study during the unveiling of a larger-than-life nativity scene in St. Peter's Square. The scene, at 23 feet high and 82 feet wide, is dedicated to the Virgin Mary, according to the Vatican's news agency.

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Thousands poured into the square and St. Peter's Basilica ahead of the Midnight Mass, which was actually held at 10 p.m. this year. Before his homily, the aging pontiff rode down St. Peter's long aisle on a wheeled platform, waving to worshipers.

Benedict will follow the Christmas Eve celebrations with his annual Christmas message "To the City and To the World" -- Urbi et Orbi in Latin -- on Sunday.