83 Christ Jesus, high priest of the new and eternal covenant, taking human nature, introduced into this earthly exile that hymn which is sung throughout all ages in the halls of heaven. He joins the entire community of mankind to Himself, associating it with His own singing of this canticle of divine praise. For he continues His priestly work through the agency of His Church, which is ceaselessly engaged in praising the Lord and interceding for the salvation of the whole world. She does this, not only by celebrating the eucharist, but also in other ways, especially by praying the divine office.
Source: Sacrosanctum Concilium (Vatican.va)