205 These, Venerable Brethren, are the subjects We desired to write to you about. We are moved to write that your children, who are also Ours, may more fully understand and appreciate the most precious treasures which are contained in the sacred liturgy: namely, the eucharistic sacrifice, representing and renewing the sacrifice of the cross, the sacraments which are the streams of divine grace and of divine life, and the hymn of praise, which heaven and earth daily offer to God.
Source: Mediator Dei (Vatican.va)