In his first address after the announcement of his intention to resign at the end of February, Pope Benedict XVI has reiterated that he lacks the strength to carry on as the leader of the world's one billion Catholics.
The 85-year-old Roman Catholic Church leader, Joseph Ratzinger, said he has decided to step down "in full freedom" and for "the good of the church."
"I am aware of the gravity of my gesture but I'm also aware of not being able to exercise the Petrine ministry with the strength it requires any longer.
"I thank you all for the prayers and the support with which you have accompanied me. Keep on praying for me, for the church and for the future pope."
His speech at the weekly general audience at a hall in the Vatican has been cheered by crowds and interrupted by resounding applauses.
The address coincided with Ash Wednesday that marks the start of Lent, a period of penitence before Easter.
Commenting on a passage of the Bible, in which Jesus resists the devil's temptations in the desert, Ratzinger somehow fuelled speculation which suggested he was at odds with other senior figures in the Vatican.
Benedict XVI warned churchmen against "submitting" Jesus to their own ambition and "exploiting God for personal glory and interests."
According to a report by Italian newspaper Corriere Della Sera, dismissed by the Vatican, Ratzinger decided to resign after reading a shocking report by a commission of three cardinals on the Vatileaks scandal.