201 Above all, try with your constant zeal to have all the faithful attend the eucharistic sacrifice from which they may obtain abundant and salutary fruit; and carefully instruct them in all the legitimate ways we have described above so that they may devoutly participate in it. The Mass is the chief act of divine worship; it should also be the source and center of Christian piety. Never think that you have satisfied your apostolic zeal until you see your faithful approach in great numbers the celestial banquet which is a sacrament of devotion, a sign of unity and a bond of love.
Source: Mediator Dei (Vatican.va)