Pope Francis has said the Roman Catholic Church, from the lowliest priest to the pontiff himself, must strip itself of all "vanity, arrogance and pride" and humbly serve the poorest members of society.
The Pope made his appeal during his visit to the central Italian town of Assisi where his namesake Saint Francis lived in the 12th century.
It comes amid a drive by Francis to turn around a Church plagued by financial and sexual abuse scandals.
"This is a good occasion to invite the Church to strip itself of worldliness," he said in a room that marks the spot where St Francis stripped naked as a young man, renounced his wealthy family and set out to serve the poor.
"There is a danger that threatens everyone in the Church, all of us. The danger of worldliness. It leads us to vanity, arrogance and pride," said Francis in the richly frescoed room of the residence of the archbishop of Assisi.
As he has often done, Francis spoke impromptu after putting aside prepared versions of two speeches, clearly moved by the sick and the poor people present in the room.
A few days after his election, he said he wanted to see "a Church that is poor and for the poor."
He has shunned the spacious papal apartments for spartan quarters in a Vatican guest house and has urged all clergy, regardless of rank, to get out among the poor and needy.
At a Mass for several thousand people outside the pink stone basilica-convent complex where St Francis is buried, the Pope appealed for respect for the environment.
"St Francis of Assisi bears witness to the need to respect all that God has created ... From this city of peace, I repeat with all the strength and the meekness of love: Let us respect creation, let us not be instruments of destruction," he said.
Francis was visibly moved when he heard the stories of some of the poor people earlier in the day.
"Many of you have been stripped by this savage world that does not give employment, that does not help, that does not care if there are children in the world who are dying of hunger, does not care if so many families have nothing to eat," he said.
He decried a world "that does not care about many people who have to flee poverty and hunger, flee seeking freedom and many times they find death, as happened yesterday in Lampedusa".
Francis was referring to the sinking of a migrant boat off the southern Italian island of Lampedusa on Thursday in which more than 300 people are believed to have died.
"Today is a day for crying," Francis said of the tragedy.