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Pope Benedict XVI, in his Palm Sunday Mass, opened the Roman Catholic Church's most solemn week by urging young people to live pure, innocent lives.

This year, Holy Week also includes the second anniversary of the April 2, 2005, death of Pope John Paul II. On Monday, the Catholic Church will close one phase of its investigation into John Paul's saintliness as it keeps up the momentum to have the beloved pope beatified.

Holding an intricately woven palm frond, Benedict opened the Palm Sunday celebration by processing through the sun-filled St. Peter's Square and up the steps of the basilica. He was preceded by dozens of priests, bishops and cardinals who clutched palms and olive branches as their red vestments fluttered in the breeze.

Palm Sunday commemorates Jesus Christ's triumphant entry into Jerusalem, and is the start of the church's Holy Week, which includes the Good Friday re-enactment of Christ's crucifixion and death and his resurrection on Easter Sunday.

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Benedict continued the tradition started by John Paul and dedicated Palm Sunday to the young, who were out in force in St. Peter's.

He told them that to follow God they should have "innocent hands and pure hearts."

"Innocent hands are hands that are not used for acts of violence," he told them. "They are hands that are not sullied by corruption and bribes."

Hearts are pure when they are not "stained by lies and hypocrisy," he said. "A heart is pure when it is estranged from the intoxication of pleasure; a heart for whom love is true and not just the passion of a moment," he said.

Benedict has an unusually busy schedule this week: In addition to the traditional Holy Week ceremonies, he will preside over a Mass on Monday afternoon in honor of John Paul to mark the second anniversary of the pontiff's death.

He is not expected to attend the ceremony earlier in the day closing the church probe into John Paul's life and virtues. That ceremony will be headed by officials of the Rome diocese, which completed the investigation that will be turned over to the Vatican to decide whether John Paul can be beatified, the last formal step before possible sainthood.

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