Holy Communion

The Eucharist is the heart and the summit of the Church's life, for in it Christ associates his Church and all her members with his sacrifice of praise and thanksgiving offered once for all on the cross to his Father; by this sacrifice he pours out the graces of salvation on his Body which is the Chruch.

-Catechism of the Catholic Church 1407
 

Then, strengthened by the body of Christ in the eucharistic communion, they manifest in a concrete way that unity of the People of God which this holy sacrament aptly signifies and admirably realizes

-Lumen Gentium 11