The Feast of the Corpus Christi is the liturgical solemnity that celebrates the reality of the Eucharist being the actual Body and Blood of Our Lord Jesus Christ, as given to man on Holy Thursday at the Last Supper by Christ Himself. It has been celebrated since the 13th century.
1 I am the living bread which came down from heaven; if any one eats of this bread, he will live for ever; and the bread which I shall give for the life of the world is my flesh.”
52 The Jews then disputed among themselves, saying, “How can this man give us his flesh to eat?”
53 So Jesus said to them, “Truly, truly, I say to you, unless you eat the flesh of the Son of man and drink his blood, you have no life in you;
54 he who eats my flesh and drinks my blood has eternal life, and I will raise him up at the last day.
55 For my flesh is food indeed, and my blood is drink indeed.
56 He who eats my flesh and drinks my blood abides in me, and I in him.
57 As the living Father sent me, and I live because of the Father, so he who eats me will live because of me.
58 This is the bread which came down from heaven, not such as the fathers ate and died; he who eats this bread will live for ever.”
Gospel: John 6:51-58
There is a great website that has a beautiful article posted on the celebration and how the Feast was instituted. A link to the page can be found here.
MOST Holy Trinity, Father, Son, and Holy Spirit, I adore Thee profoundly. I offer Thee the Most Precious Body, Blood, Soul, and Divinity of Jesus Christ, present in all the tabernacles of the world, in reparation for the outrages, sacrileges, and indifference by which He is offended. And through the infinite merit of His Most Sacred Heart, and the Immaculate Heart of Mary, I beg of Thee the conversion of poor sinners.
Happy Feast Day!