Aside from written texts, the Pope Emeritus last spoke in public on June 28, 2016.
Standing alongside Pope Francis at a ceremony in the Vatican to mark the 65th anniversary of his ordination to the priesthood on June 29, 1951, Benedict XVI developed a short but profound meditation on the meaning of the word "Eucharist" and its Greek etymology through the word "Eucharistòmen," which means "thank you."
The last sentence pronounced by Benedict XVI in front of a microphone is somehow charged with a particular value:
Finally, we wish to insert ourselves into the “thanks” of the Lord, and thus truly receive the newness of life and contribute to the “transubstantiation” of the world so that it might not be a place of death, but of life: a world in which love has conquered death.
Apart from thanking the organizers of the event, and especially Pope Francis, Benedict XVI's public and official visibility thus ended with the phrase "love has conquered death."