Benedict XVI pledged "unconditional obedience" to the next pope in his final meeting with the cardinals who will pick his successor after he stands down later Thursday.
"I will continue to serve you in prayer, in particular in the coming days" as the cardinals work to select a new pontiff, he said.
After nearly eight tumultuous years at the head of the world's 1.2 billion Catholics, Benedict XVI has made the almost unprecedented decision to resign effective 8 p.m. (2 p.m. ET).
His words to the cardinals appeared designed to answer concerns that the presence of a former pontiff might lead to confusion or competing loyalties once the new pope is installed.
Benedict told the cardinals it was a "joy to walk with you" during his eight years as pope.
Vatican spokesman the Rev. Thomas Roscia said 144 cardinals had attended Benedict XVI's farewell to them as pope.
That includes both cardinal-electors, who are under the age of 80, and cardinals who are not eligible to vote for the next pope.
Not all those eligible to vote were present, said Vatican spokesman the Rev. Federico Lombardi.
The final number of cardinal-electors has not been confirmed but is thought to be 115.
The cardinals gave Benedict a standing ovation, and then one by one each met the pope to say a final few words.
Cardinal Roger Mahony, the retired archbishop of Los Angeles, tweeted after the event that he had asked the pope to pray for the people of Los Angeles.
"He grasped my hand and said 'Yes'!!" Mahony said.
The current Catholic archbishop in Los Angeles earlier this month disciplined Mahony for his mishandling of "painful and brutal" allegations of sexual abuse by priests. Mahony's decision still to travel to Rome to take part in the election of the new pope has been controversial.
Benedict's last day in office has been carefully mapped out by Vatican aides who've had to make up the rules over the past two weeks.
In contrast to the public focus of his final general audience and meetings with foreign dignitaries Wednesday, Benedict is spending Thursday in a quiet, more intimate manner.
Later, senior Vatican officials and a detachment of the Swiss Guards, who by tradition protect the pope, will gather to bid him farewell as his helicopter takes off from Vatican City bound for the summer papal residence, Castel Gandolfo.
Once at Castel Gandolfo, where he will spend the next few weeks before moving to a small monastery within the Vatican grounds, Benedict will make one last public appearance on the balcony.
Having greeted those gathered below, he will step back inside and begin his life of seclusion.
At 8 p.m., the Swiss Guards will ceremonially leave the residence's gate -- and the process of transition to a new pope will begin.