The Holy Father said this Wednesday at the end of the general audience held in St. Peter's Square, when greeting participants in the Italian national congress of the Apostleship of Prayer.
The meeting commemorated the 50th anniversary of the publication of Pius XII's encyclical "Haurietis Aquas," which greatly stimulated devotion to the Sacred Heart of Jesus.
"May union with the Heart of Jesus be, for all, a source of holiness and effective apostolic action," said Benedict XVI.
The congress of the Apostleship of Prayer gathered 500 delegates from various dioceses of Italy this week in Rome.
Father Massimo Taggi, national director of the Apostleship of Prayer, said the meeting confirmed "the urgency of a return to interiority which responds to a widespread and profound expectation of our society."
"Today's world is in urgent need of spirituality," he said at the opening of the working sessions.
"Spirituality," the director said, "is the concrete response to one of the greatest urgencies of our society, involved in a subtle and powerful process which is no longer of secularization but of genuine atheist and materialist secularism."
The Apostleship of Prayer began among Jesuit students in France led by Father Francis Xavier Gautrelet in 1844.
Today, the Apostleship of Prayer has spread worldwide and has at least 50 million members. It is estimated that 100 million people make the daily offering.