Pope Francis gave 300 homeless people and refugees a sandwich and a drink to thank them for helping to hand out pamphlets at an Epiphany feast day service on Friday.

The picnic, announced by the Pope's charity office, was the latest gesture from the leader of the world's 1.2 billion Catholics to the needy, whose plight he has made a central cause of his papacy.

Francis has ordered showers for the homeless to be set up just off St Peter's Square, and treated 1,500 to Neapolitan pizza after the canonisation of Mother Teresa last year.

On January 6 Christians celebrate the Epiphany, the biblical story of wise men who travel from the East, following a star, to find the baby Jesus.

Speaking from the window of the Vatican's Apostolic Palace, Francis compared the gifts the wise men – or Magi – are believed to have brought to Jesus to the pamphlets handed out to the roughly 35,000 faithful in St Peter's Square.

"I thought I would give you a little gift too. The camels are missing but I will give you the gift," he said. "I wish you a year of justice, forgiveness, serenity, but above all mercy. Reading this book will help – it fits in your pocket!"

Earlier Francis had celebrated mass in St Peter's Basilica. In his homily on the coming of the Magi he quoted St John Chrysostom, saying that "the Magi did not set out because they had seen the star, but they saw the star because they had already set out. Their hearts were open to the horizon and they could see what the heavens were showing them, for they were guided by an inner restlessness. They were open to something new."

He contrasted their approach with that of Herod, who was "anaesthetised by a cauterised conscience. He was bewildered, afraid. It is the bewilderment which, when faced with the newness that revolutionises history, closes in on itself and its own achievements, its knowledge, its successes. The bewilderment of one who sits atop his wealth yet cannot see beyond it."

He concluded: "The Magi were able to worship, because they had the courage to set out. And as they fell to their knees before the small, poor and vulnerable Infant, the unexpected and unknown Child of Bethlehem, they discovered the glory of God."

Additional reporting by Reuters.