The saints were Christians who were "crazy for concreteness," knowing that faith is not an idea, but a relationship with Jesus, which leads to actions that demonstrate love, Pope Francis said.
Celebrating morning Mass Jan. 7 in the chapel of the Domus Sanctae Marthae, the pope said the celebration of Christmas is the celebration of a faith that is concrete.
Christians profess their belief that "the son of God came in the flesh, became one of us," he said. "He was conceived in the womb of Mary, born in Bethlehem, grew like a baby does, fled to Egypt, returned to Nazareth, learned to read with his father, to work" — although God, he was also truly human.
The first reading at Mass was a passage from the First Letter of John, which says Christians are commanded to believe in the name of Jesus and love one another, with "concrete love, not a fantasy love," the pope said.
"Concreteness. This is the challenge," he said. "Not ideas and beautiful words."
The first reading at Mass also included John's admonition: "Do not trust every spirit but test the spirits to see whether they belong to God, because many false prophets have gone out into the world."
The Christian life entailed 'spiritual vigilance' as well as faith in Jesus Christ and in charity.
One way to grow in the art of spiritual vigilance was to take several minutes at the end of each day to communicate with God and to ask him to speak to one's heart.
The next step was to follow up on the resulting inspiration by consulting Scripture and a wise spiritual guide.
There were many people — priests, religious, laity — with the ability to "help us see what is happening in our spirit so we do not err."
Pope Francis said at the end of his homily that Jesus became human, born of a woman, who suffered a real death and asked us to love our brothers and sisters concretely even if some of them are not easy to love.