No longer servants, but friends (Jn 15:15): A theological approach to friendship in the light of the mystery of Christ. This doctoral thesis aims to highlight the philia offered by Christ to his friends as a sure path for the process of renewal of human relationships, above all, in Christian communities. From a theological liturgical reading, the friendship that was studied translates the model of the Covenant that God offers to all humanity that seeks an existential experience of love, portrayed in its historical-salvific and liturgical-celebrative content. For such, this thesis has its foundation in the Biblical Revelation of God as the Friend, who creates the human being to live in his friendship. The latter, even if he refuses it, is supported by God, who never abandons him to the power of death. In the New Covenant, the Risen Christ allows love, in its expression of friendship, to be reread to become the archetype of the new relationship between Jesus and his disciples, by uniting the act of giving life to the philia. The Liturgy, in turn, as a source of life, prayer and friendship, brings Christians back to the culmen et fons of the authentic spirituality of the Church, as it invites them to participate fully in the celebratory act which, in the Eucharist, fulfills its maximum community expression, lived in the heart of the Church. In this salvific-celebrative context, the mystery of Christ yearns to bear fruit in the life of every Christian, generating a new understanding of the liturgy: a salvific-celebrative act performed among friends, in which the presence of the Risen is recognized and celebrated as a memorial and anticipation of the Celestial Liturgy; human action is deified, and its action consists of gestures of mutual friendship (Redemption) that favor coexistence in the joy of the Covenant. This experience can represent a relevant contribution to the renewal of the Christian community, in which the liturgy, by revealing itself as a school of friendship and hospitality, is also relevant in new digital spaces, in order to encourage its users to a communion in digital relationships and educate them to raise awareness of the value of meeting friends in person. Such effective realization takes place through a liturgical assembly. When rescuing this theme under the prism of Eucharistic Prayer IV of the Roman Missal, Christian friendship is reread as a process, at the same time, affective and real of the celebrated mystery. In this way, it is concluded that, when a liturgical celebration assumes its authentic character of service, in the Christological context of friendship, a spark is lit that is capable of reanimating and infusing in the community the supernatural strength of a philia that allows each Christian to lean on the Friend s chest.