The observance of Corpus Christi, sometimes called Corpus Domini (The Body of the Lord). In places like Rome, the traditional day to observe this feast is Thursday, connecting with Holy Thursday. A portion of the Pope’s homily is noted below (the full text is here).
… the sacredness of the Eucharist. Also here we heard in the recent past of a certain misunderstanding of the authentic message of Sacred Scripture. The Christian novelty in regard to worship was influenced by a certain secularist mentality of the 60s and 70s of the past century. It is true, and it remains always valid, that the center of worship is now no longer in the rites and ancient sacrifices, but in Christ himself, in his person, in his life, in his paschal mystery. And yet, from this fundamental novelty it must not be concluded that the sacred no longer exists, but that it has found its fulfillment in Jesus Christ, incarnate divine Love. The Letter to the Hebrews, which we heard this evening in the Second Reading, speaks to us precisely of the novelty of the priesthood of Christ, “high priest of the good things that have come” (Hebrews 9:11), but it does not say that the priesthood is finished. Christ “is the mediator of a new covenant” (Hebrews 9:15), established in his blood, which purifies our “conscience from dead works” (Hebrews 9:14). He did not abolish the sacred, but brought it to fulfillment, inaugurating a new worship, which is, yes, fully spiritual but which however, so long as we are journeying in time, makes use again of signs and rites, of which there will be no need only at the end, in the heavenly Jerusalem, where there will no longer be a temple (cf. Revelation 21:22). Thanks to Christ, the sacred is more true, more intense and, as happens with the Commandments, also more exacting! Ritual observance is not enough, but what is required is the purification of the heart and the involvement of life.
Pope Benedict XVI
Corpus Christi at the Basilica of St. John Lateran
7 June 2012