At the end of today's Easter Gospel (Luke 24:35-48) Christ says to the Apostles "You are the witnesses of these things." Meaning
1. An eye-witness: you have seen and touched and therefore believe (two senses here: the original apostles; and our experiencing Christ, in the life of the Church).
2. You are to proclaim it to the world! Jesus Christ is risen! He is the Savior! The Messiah! The promised One from heaven, for the forgiveness of sins in His name.
3. You are to give your life for Him! The Greek word for witness became our the Church's word (in Latin) for the ultimate witness: martyrdom. He says, "you are to be martyrs of these things."
Pope Emeritus Benedict is contemplating death, preparing for a happy death, preparing to see the Lord, as every good Christian is obliged to do. That's witnessing to Christ crucified and risen from the dead. Those who live in Him have died in Him and so live eternally. To die in Christ is to live, to really live!
In Latin the phrase to give witness is testes dare, which also means "to give you head", which also has a fourfold meaning: testifying, at the peril of your life, using your intelligence (your head), and perhaps a loose allusion to chastity (in antiquity "to testify" meant to swear on one's testicles (e.g. Abraham does this) [notice the same root word]).
Long live the great Emeritus Pope who was chosen today to give his life as Pope, to bear witness to Christ, in all meekness and humility, true magnanimity! worthy of the ancient witnesses, worthy of Christ our blessed and crucified Lord! Life! True Life!
Regarding living testimony, Joseph Ratinger stated that it was the life of the Church from which he received faith in Jesus Christ: the witness of the Church's life and worship in which he was nurtured.
"How Jesus Christ entered my life: I met him first, not in literature or philosophy, but in the faith of the Church. That means that from the beginning he was not, for me, an important figure from the past (like Plato or Thomas Aquinas, for example), but someone who lives and works today, someone whom we can meet today. It means, above all, that I have learned to know him within the history of the Faith that originates in him , to see him as faith sees him in its most enduring formulation by the Council of Calcedon:...Son of God, possessed of one nature with God and one nature with us..."
Co-Workers, 130-131