In his homily, Francis reminded the inmates that his gesture of washing their feet re-enacted the revolutionary gesture of Jesus washing the feet of his disciples before he was crucified, essentially doing the work of a slave out of love.
"If you can do something, a service for your companions in prison, do it," Francis urged them during his homily. "This is love. This is like washing feet: to be the servant of others."
It's the third Holy Thursday that Francis has spent at a detention center, part of his long-standing emphasis on ministering to prisoners and the need to give them rehabilitation and hope.
"The Holy Father gave us message not just of hope, but he told us that the love of God is great and is ready to forgive everyone," prison director Nadia Cersosimo told Vatican Radio.
Because of the nature of the prison, its inmates and their families, Francis' visit was conducted under unusually strict privacy: Vatican Radio only aired edited excerpts of his homily after the fact, and the Vatican's television service planned edited TV footage. Usually the pope's activities are covered live by at least Vatican TV and radio, if not independent media.
Paliano has 60 to 70 inmates, including about 50 mafia turncoats. The prison also houses four women and has a special ward for tuberculosis-infected inmates.
The Vatican said three of the 12 inmates who had their feet washed are women and one is a Muslim who is due to be baptized a Christian in June. Prisoners prepared cakes as gifts and offered the pope zucchini and cucumbers from the prison's organic garden.
In an interview published Thursday in Rome daily La Repubblica, Francis said his emphasis on reaching out to inmates comes from his heart, as well as the biblical imperative to visit prisoners and accompany the least of society.
"When I'm looking at a prisoner, I ask myself: 'Why him and not me?'" he said. "'Why did he fall and not me?' It's a mystery that brings me closer to them."
Francis opened the most solemn period of the Catholic Church's liturgical calendar by celebrating Mass on Thursday morning in St. Peter's Basilica before heading to Paliano. On Friday, he participates in the torch-lit procession at Rome's Colosseum re-enacting Christ's crucifixion.
Saturday brings the late-night Easter vigil, with Easter Sunday Mass the following day.