Tens of thousands of pilgrims have attended St Peter's Square in Rome for one of the final public appearances of Pope Benedict XVI.
He is stepping down on 28 February.
The Pope recited the Angelus prayer and thanked all those who had prayed for him and shown him support over the past few days since his resignation.
The Vatican has said it may hold the conclave that chooses the new pope early, so he can be in place before the start of Holy Week on 24 March.
Vatican accommodation
The Pope appeared at his study window overlooking St Peter's Square at 11:00 GMT, his first such appearance since announcing his resignation last Monday.
The crowd erupted into loud applause and there were chants of "Long live the Pope".
One banner in the square read: "We love you".
The Pope used his Angelus appearance to urge the faithful to "renew" and "refocus" on God.
He said: "The Church calls on all its members to renew themselves... which constitutes a fight, a spiritual battle, because the evil spirit wants us to deviate from the road towards God."
The pope spoke in a number of languages; speaking in Spanish, he said: "I beg you to continue praying for me and for the next pope."
The BBC's David Willey in Rome says that after the prayer recital on Sunday the Pope plans to spend the rest of the week on a Lenten prayer retreat closeted inside the Apostolic Palace with senior cardinals and bishops.
He says the retreat will be a time of reflection about what Pope Benedict's eight-year long papacy has achieved and what are the priorities now facing a Church whose credibility has been seriously harmed by clerical sex abuse scandals.
Vatican spokesman Federico Lombardi said earlier: "The Pope is living through these days calmly even though they're very emotional and packed."
The Vatican said on Saturday it was considering calls from cardinals to hold the papal conclave earlier than planned, to have a pontiff in place before Holy Week, the most important event in the Christian calendar.
Under current rules, the vote cannot be held before 15 March, to give cardinals enough time to travel to Rome. The Vatican is examining the possibility of changing the rule.
After his spiritual retreat, the Pope will have very few public engagements.
He is scheduled to receive Italian President Giorgio Napolitano on 23 February.
The Pope will then celebrate Angelus again on 24 February and hold a final audience in St Peter's Square on 27 February.
Pope Benedict will be flown to his summer residence of Castel Gandolfo on 28 February and remain there as accommodation in the Vatican is prepared.
At 19:00 GMT on 28 February he will no longer by pope.
One Vatican official told Reuters news agency it was "absolutely necessary" that Benedict lived in the enclave, "otherwise he might be defenceless".
"He wouldn't have his immunity, his prerogatives, his security, if he is anywhere else," the official said.
There are concerns he could be cited in relation to legal cases connected with alleged sexual abuses by Catholic Church officials.
The 85-year-old pontiff announced his shock resignation last Monday, citing his advanced age as the reason for stepping down.
The last pontiff to resign was Pope Gregory XII, who quit in 1415 amid a schism within the Church.
