Pope Francis took on the role of a simple parish priest on Sunday, saying Mass for the Vatican's resident community and urging listeners to not to be so quick to condemn others for their failings.
Francis, the former Cardinal Jorge Bergoglio, said Mass for a few hundred people in Santa Anna, a church just inside the Vatican walls that is used as the parish church for workers in the city-state.
Before he entered the tiny church, Francis stopped to greet cheering well-wishers who had lined up outside a nearby Vatican gate shouting "Francesco, Francesco, Francesco," his name in Italian.
He chatted and laughed with many of them before pointing to his black plastic wrist watch and saying: "It's almost 10 o'clock. I have to go inside to say Mass. They are waiting for me."
Wearing the purple vestments of the liturgical season of Lent, which ends in two weeks on Easter Sunday, he delivered a short homily in Italian, without notes, centred on the gospel story of the crowd that wanted to stone a woman who had committed adultery.
Jesus told them "let him among you who is without sin, cast the first stone" and then told the woman "go and sin no more".
"I think even we are sometimes like these people, who on the one hand want to listen to Jesus, but on the other hand, sometimes we like to stone others and condemn others. The message of Jesus is this: mercy," he said.
"I say in all humility that this is the strongest message of the Lord: mercy," Francis said, speaking in a soft voice.
The pope, who was due to give his first Sunday address and blessing from the window of the papal apartments to tens of thousands in St. Peter's Square, said people should be open to God's mercy, even those who have committed grave sins.
"The Lord never tires of forgiving, never! It is we who tire of asking for forgiveness," he said.
"Let us ask for the grace of never tiring of asking for forgiveness because he never tires of forgiving," he said.
At the end of the Mass, he waited outside the church and greeted people as they left the building, like a parish priest.
He asked many of them as they emerged: "Pray for me".