Pope St. Paul VI, Encyclical Mysterium fidei/On the Mystery of Faith
The Mystery of Faith, that is, the ineffable gift of the Eucharist that the Catholic Church received from Christ, her Spouse, as a pledge of His immense love, is something that she has always devoutly guarded as her most precious treasure, and during the Second Vatican Council she professed her faith and veneration in a new and solemn declaration. (cf. Constitution on the Sacred Liturgy, 47)
Pope St. John Paul II, Encyclical Ecclesia de eucharistia/Church of the Eucharist
The Church draws her life from the Eucharist. This truth does not simply express a daily experience of faith, but recapitulates the heart of the mystery of the Church.
Ibid., Holy Thursday Letter Dominicae cenae (On the Mystery and Worship of the Eucharist)
. . . the ministerial and hierarchical priesthood, the priesthood of the bishops and the priests, and, at their side, the ministry of the deacons—ministries which normally begin with the proclamation of the Gospel—are in the closest relationship with the Eucharist. The Eucharist is the principal and central raison d'etre of the sacrament of the priesthood, which effectively came into being at the moment of the institution of the Eucharist, and together with it. Not without reason the words "Do this in memory of me" are said immediately after the words of eucharistic consecration, and we repeat them every time we celebrate the holy Sacrifice.
Pope Benedict XVI, Apostolic Exhortation Sacramentum Caritatis/Sacrament of Charity
The sacrament of charity, the Holy Eucharist is the gift that Jesus Christ makes of himself, thus revealing to us God's infinite love for every man and woman. This wondrous sacrament makes manifest that "greater" love which led him to "lay down his life for his friends" (Jn 15:13). . . . In the sacrament of the altar, the Lord meets us, men and women created in God's image and likeness (cf. Gen 1:27), and becomes our companion along the way. In this sacrament, the Lord truly becomes food for us, to satisfy our hunger for truth and freedom.
Pope Francis, Wednesday Audience, ”The Summit of God’s Saving Action” (2/5/2015)
Wednesday Audience, “The Identity of the Church Flows from the Eucharist” (2/12/2015)