Catechism of the Catholic Church §995 — excerpt
To be a witness to Christ is to be a "witness to his Resurrection," to "[have eaten and drunk] with him after he rose from the dead."
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.