The retreat for the 85-year-old leader of the Roman Catholic church was planned long before he announced his resignation, ANSA reported.
It will end Feb. 23, when the pope is scheduled to meet Italian President Giorgio Napolitano.
In the interim, the usual Wednesday general audiences have been cancelled.
Benedict gave his last Angelus mass on Sunday. He will step down Feb. 28.
The archbishop of New York, Timothy Dolan, says the church should not be in a rush to replace Benedict.
He says the 117 cardinals who will elect the next pope should take their time.
Noting there are "many delicate questions to address," Dolan said, "I don't think we want to rush the conclave. The important thing (now) is to be here, express our love and best wishes for Pope Benedict, pray together and then make the decisions."
Vatican spokesman Father Federico Lombardi said during the weekend the conclave could start before the pope steps down because he had not died, but quit.