"Thank you for having given us the luminous example of the simple and humble worker in the vineyard of the Lord," Bertone said, quoting Benedict's own words when he first appeared on the loggia overlooking St. Peter's Square after he was elected pope.
"Viva il papa!" the crowd yelled as Benedict stepped off the altar.
Ash Wednesday marks the start of Lent, the most solemn season on the church's liturgical calendar that ends with Holy Week, when the faithful commemorate the death of Christ and his resurrection on Easter Sunday. By this Easter, on March 31, the church will likely have a new pope.
The scene was festive earlier in the day, when Benedict took the extraordinary step of speaking directly to his flock about why he had broken with 600 years of tradition and decided to retire on Feb. 28.
"As you know, I have decided to renounce the ministry that the Lord gave to me on April 19, 2005," Benedict said, to warm applause. "I did this in full liberty for the good of the church."
He thanked the faithful for their prayers and love, which he said he had "physically felt in these days that haven't been easy for me." And he asked them to "to continue to pray for me, the church, and the future pope."
Benedict looked tired but serene as he basked in a standing ovation when he entered the packed hall for his traditional Wednesday catechism lesson. His speech was interrupted repeatedly by applause, and many in the audience of thousands had tears in their eyes.
A huge banner reading "Grazie Santita" (Thank you Your Holiness) was strung up at the back of the room and a chorus of Italian schoolchildren serenaded him with one of his favorite hymns in German a gesture that won over the pope, who thanked them for singing a piece "particularly dear to me."
He appeared wan and spoke very softly, but his eyes twinkled at the flock's welcome warm and heartfelt if somewhat bittersweet.
"He gave us eight wonderful years of his words," said Ileana Sviben, an Italian from the northern city of Trieste who couldn't hide her sadness. "He was a wonderful theologian and pastor."
The Rev. Reinaldo Braga Jr., a Brazilian priest studying theology in Rome, said he, too, was saddened when he first heard the news.
"The atmosphere was funereal but nobody had died," he said. "But then I realized it was a wise act for the entire church. He taught the church and the world that the papacy is not about power but about service."
It was a sentiment the retiring Benedict himself emphasized Wednesday when he told his flock that the "path of power is not the road of God."
Benedict is the first pope to resign in nearly 600 years, and the decision has placed the Vatican in uncharted waters: No one knows what he'll be called or even what he'll wear after Feb. 28.
The Vatican, however, revealed some details of his final day as pope, saying he would attend a morning farewell ceremony with his cardinals and then fly off by helicopter at 5 p.m. to the papal summer retreat at Castel Gandolfo.
Under that timetable, Benedict will be far from the Vatican when he ceases being pope at 8 p.m. a deadline decided by Benedict himself because that's when his normal workday ends.
Vatican spokesman the Rev. Federico Lombardi said no formal or symbolic act was needed to make his resignation official at that time, because Benedict has already done all that was required to resign by affirming publicly he had taken the decision freely.
Benedict's final official acts as pope will include audiences with the Romanian and Guatemalan presidents this week and the Italian president on Feb. 23.
Making sure the transition goes smoothly, Benedict made an important appointment Wednesday, naming the No. 2 administrator of the Vatican city state, Monsignor Giuseppe Sciacca, as a legal adviser to the camerlengo.
The camerlengo, or chamberlain, helps administer the Vatican bureaucracy in the period between Benedict's resignation and the election of a new pope. The current camerlengo is Bertone, the Vatican secretary of state.
He and the dean of the College of Cardinals, his predecessor Cardinal Angelo Sodano, will have a major role in organizing the conclave, during which the 117 or so cardinals under the age of 80 will vote on who should succeed Benedict.
The Vatican has made clear that Benedict will play no role in the election of his successor, and once retired, he will be fully retired. He plans to live a life of prayer in a converted monastery on the far northern edge of the Vatican gardens.
But his continued physical presence within the Vatican walls has raised questions about how removed he really will be from the life of the church. Lombardi acknowledged that Benedict would still be able to see his friends and colleagues.
"I think the successor and also the cardinals will be very happy to have very nearby a person that best of all can understand what the spiritual needs of the church are," Lombardi said.
Benedict is expected, however, to keep a low public profile.
As a result, Benedict's final public appearances his last general audience will be Feb. 27 are expected to draw great crowds, as they may well represent some of the last public speeches for a man who has spent his life as a priest, a cardinal and a pope teaching and preaching.
And they will also give the faithful a way to say farewell under happier circumstances than when his predecessor, Pope John Paul II, died in 2005.