Thanking them for the enormous turnout in his support, he said that the Church must root herself in God to combat the "true enemy" of sin inside and outside of the Church.
Estimates in the Holy See's Press Office put the number in attendance in St. Peter's Square at more than 150,000 people, many there with Italian lay associations and holding balloons and banners with supportive messages for the Pope.
A multitude of flags from other countries such as India, Poland and Brazil were also prominent in the crowd, which spilled out of the Square and down the street, called Via della Conciliazione, where big screens were set up in anticipation of such a turnout.
Pope Benedict XVI greeted the masses, saying, "Thank you! Thanks for your presence and confidence!"
He welcomed the president of the Italian bishops, Cardinal Angelo Bagnasco, and all those who had answered the invitation from a national association of lay groups, CNAL, which, on April 14, called for a massive show of support for the Pope and his work.
"Dear friends," Benedict XVI told them, "today you demonstrate the great affection and the deep closeness of the Church and of the Italian people to the Pope and to your priests," whom, he explained, take care of the faithful "so that through moral and spiritual renewal we can always better serve the Church, the People of God and all who turn to us with trust."
"The true enemy to fear and to combat is sin," he added, noting that this also affects members of the Church. Being "in the world but not of the world," he explained, Christians do not fear the world "but we must guard ourselves from its seductions.”
"We must, rather, fear sin and for this be strongly rooted in God, solid in the good, in love and in service."
This, he added, is what the Church, her priests and faithful "have done and continue to do with fervid commitment for the spiritual and material good of the people in every part of the world." Christians "serve God and man in the name of Christ."
Looking to the future, he said, "we continue this path together with trust." He prayed that trials push us to be more deeply rooted and coherent.
Concluding his remarks, the Holy Father renewed the call he had made in Fatima last week and called for prayer through the intercession of Mary for the conversion of hearts.
Also taking part in Sunday's Regina Coeli by way of massive television screens set up in the square in front of the Basilica of St. John Lateran was Cardinal Vicar of Rome Agostino Vallini and a large group of immigrants celebrating the "Festival of Peoples."
SIC: CNA