Francis described this as an "example to follow" for everyone. He also stressed that the faithful should not be "weak" or "remote-controlled Christians, incapable of creativity."
Benedict is now living in a Vatican monastery. A theologian, Benedict has said he wants to dedicate the rest of his life to prayer and meditation.
Benedict was a longtime Vatican-based German cardinal and already elderly when elected in 2005 to succeed Pope John Paul II.
Benedict had worked closely with John Paul, who began his long papacy in 1978 as a vigorous, athletic middle-aged man but who later was slowed by Parkinson's disease, which increasingly enfeebled him in his last years before death.