"The Angelic Doctor also notes that the 'effect of this sacrament is the unity of the mystical body [the Church], without which there can be no salvation. Therefore it is necessary to receive the Eucharist, at least by desire (in voto), in order to be saved' (III, q. 73, a. 1, ad 2). These words [...]
At every celebration of the Eucharist, we are spiritually brought back to the paschal Triduum: to the events of the evening of Holy Thursday, to the Last Supper and to what followed it. Source: Pope St. John Paul II, General Audience, September 13, 1989
"The Eucharist is the source of the Christian life because whoever shares in it receives the motivation and strength to live as a true Christian. Christ's sacrifice on the cross imparts to the believer the dynamism of his generous love. The Eucharistic banquet nourishes the faithful with the Body and Blood of the divine Lamb [...]
"At the center of the Church is the Eucharist, where Christ is present and active in humanity and in the whole world by means of the Holy Spirit." Source: Pope St. John Paul II, General Audience, September 13, 1989
"In the Eucharist Christ gives us his body and blood as food and drink, under the appearance of bread and wine, just as during the paschal meal at the Last Supper. Only through the Spirit, the giver of life, can the Eucharistic food and drink produce in us 'communion,' that is to say, the salvific [...]
"In the Eucharist - on each occasion - there is re-presented the sacrifice of the Body and Blood offered by Christ once for all on the cross to the Father for the redemption of the world." Source: Pope St. John Paul II, General Audience, September 13, 1989
"We are well aware that from the earliest times the celebration of the Eucharist has been linked not only with prayer but also with the reading of Sacred Scripture and with singing by the whole assembly. As a result, it has long been possible to apply to the Mass the comparison, made by the Fathers, [...]
"In it is present 'the blood of Christ, who through the eternal Spirit offered himself without blemish to God' (Heb 9:14); the blood 'poured out for many' (Mk 14:24) 'for the forgiveness of sins' (Mt 26:28); the blood 'which purifies your conscience from dead works' (cf. Heb 9:14); the 'blood of the covenant' (Mt 26:28). [...]
"The one who lives in this way, 'according to the flesh,' that is, who subjects himself – even if not altogether consciously, nevertheless effectively – to the threefold concupiscence, particularly to the concupiscence of the flesh, ceases to be capable of this freedom for which 'Christ has set us free'; he also ceases to be [...]
"Jesus had said in one of his parables: 'The kingdom of heaven may be compared to a king who gave a marriage feast for his son' (Mt 22:2). The Eucharist is the sacramental anticipation and, in a certain sense, a 'foretaste' of that royal feast which the Book of Revelation calls 'the marriage supper of [...]