The Sacred Heart of Jesus wishes to welcome all into 'a revolution of tenderness' through life-changing prayer, Pope Francis said Friday, while insisting that "the heart of the Church's mission is prayer."

"The Heart of Christ is so great that it wishes to welcome us all into the revolution of tenderness. The closeness to the Heart of the Lord urges our hearts to approach their brother with love, and helps to enter into this compassion for the world," Pope Francis said June 28, the Solemnity of the Sacred Heart of Jesus.

Francis addressed 6,000 members of the Pope's Worldwide Prayer Network on the occasion of the 175th anniversary of its founding. The network aims to mobilize Catholics through prayer to address the challenges facing humanity and the mission of the Church.

"It is good, on this day of the solemnity of the Sacred Heart of Jesus, to remember the foundation of our mission," Pope Francis said. "It is a mission of compassion for the world, we could say a 'journey of the heart,' that is, a prayerful journey that transforms people's lives."

"We are called to be witnesses and messengers of God's mercy, to offer the world a perspective of light where darkness is, of hope where despair reigns, of salvation where sin abounds," the pope told the prayer network in the Vatican's Paul VI Hall.

"To enter into prayer is to enter with my heart into the heart of Jesus, to make a way inside the heart of Jesus, what Jesus feels, the feelings of compassion of Jesus, and also to make a journey inside my heart to change my heart in this relationship with the heart of Jesus," he explained.

Pope Francis urged the importance of teaching children to pray, and said that it pains him to see so many children who do not even know how to make the sign of the cross.

"Teach children to pray. Because they immediately reach the heart of Jesus, immediately. Jesus wants them," he said.

The pope also stressed the importance of intercessory prayer saying that all Catholics are called to pray for "the people who stand beside us … assuming their joys and sufferings in prayer."

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"The Bible tells us that Jesus is before the Father and intercedes for us. He is our intercessor, and we must imitate Jesus. Be intercessors," he said.

"Throughout history, the greatest men and women of God have been intercessors like Jesus," he added.

"The Apostolate of Prayer, with its worldwide network of prayer for the Pope and in communion with him, reminds us that the heart of the Church's mission is prayer," Pope Francis said, repeating, "The heart of the Church's mission is prayer."