A favorite line of Pope Paul VI’s that later popes that have quoted in their own teaching comes from the Apostolic Exhortation Evangelii Nuntiandi (Dec. 8, 1975). In No. 41, Pope Paul VI observes that “Modern man listens more willingly to witnesses than to teachers, and if he does listen to teachers, it is because they are witnesses.”

I haven’t performed a systematic search of later papal citations of this observation, but one that I came across recently was in remarks related to evangelization given by Pope Benedict XVI on September 23, 2006:

To you, Pastors of God’s flock, is entrusted the mandate of safeguarding and transmitting faith in Christ, passed on to us through the living tradition of the Church and for which so many have given their lives. To carry out this task, it is essential that first of all you show you are “in all respects a model of good deeds, and in your teaching show integrity, gravity and sound speech that cannot be censured” (Ti 2: 7-8).

“Modern man”, wrote my Predecessor of venerable memory, the Servant of God Pope Paul VI, “listens more willingly to witnesses than to teachers, and if he does listen to teachers, it is because they are witnesses” (Apostolic Exhortation Evangelii Nuntiandi, n. 41).