When he resigned, Benedict cited his advanced age as the reason, saying he no longer had the strength for "an adequate exercise of the Petrine ministry".

BBC: Ex-Pope Benedict returns to Vatican

After having repeatedly examined my conscience before God, I have come to the certainty that my strengths, due to an advanced age, are no longer suited to an adequate exercise of the Petrine ministry.

CNN: Full text of Pope Benedict XVI's declaration

"After having repeatedly examined my conscience before God, I have come to the certainty that my strengths, due to an advanced age, are no longer suited to an adequate exercise of the Petrine Ministry, " he added.

WSJ: Pope Benedict XVI to Resign

"After having repeatedly examined my conscience before God, I have come to the certainty that my strengths due to an advanced age are no longer suited to an adequate exercise of the Petrine ministry, " he told the cardinals.

NPR: Pope Resigning On Feb. 28, Conclave In March

Addressing the clergy who had joined him, he thanked them "not only for this week, but for these past eight years that you have carried with me -- with great skill, affection, love and faith -- the weight of the Petrine ministry, " referring to the papacy.

CNN: February 23, 2013 -- Updated 1735 GMT (0135 HKT)

"After having repeatedly examined my conscience before God, I have come to the certainty that my strengths, due to an advanced age, are no longer suited to an adequate exercise of the Petrine Ministry, " the pope said in a declaration in Latin to a gathering of cardinals on Monday.

WSJ: Pope Benedict XVI to Resign