Jesus is "the greatest and most expressive form of this love," he said, explaining that the Lord's entire life and being "are nothing other than the concrete revelation of the Father's love, reaching its highest expression on the Cross."
Addressing the participants directly, Pope Francis said they as volunteers and workers of mercy "are among the most precious things the Church has."
By working silently every day in service to others, "(you) give shape and visibility to mercy. You express one of the most noble desires of the human heart, making a suffering person feel loved."
He told the workers and volunteers to never forget that they "touch the flesh of Christ" with their own hands daily in their work and encouraged them to be generous in solidarity.
"The world stands in need of concrete signs of solidarity, especially as it is faced with the temptation to indifference," he said, noting how true solidarity requires people who are ready to "defy such individualism, which is the tendency to think only of oneself and to ignore the brother or sister in need."
In addition to going beyond individualism and indifference, Francis urged the volunteers to "always (be) happy and full of joy" in their service, but cautioned them "never presume to think that you are superior to others."
"Instead, let your work of mercy be a humble and eloquent continuation of Jesus' presence who continues to bend down to our level to take care of the ones who suffer."
Pope Francis concluded his address noting how he will proclaim Mother Teresa a saint tomorrow, Sept. 4, adding, "She deserves it!"
Mother Teresa's witness to mercy, he said, "will join the vast array of men and women who, by their holiness of life, have made the love of Christ visible."
"Let us also imitate their example, as we ask to be humble instruments in God's hands in order to alleviate the world's sufferings, and to share the joy and hope of the resurrection," he said, and closed by leading pilgrims in a moment of silent prayer for all those who are suffering, for the indifferent, and for the volunteer and workers "who go out to encounter the flesh of Christ."