"The nuns should keep before their eyes by day and by night Christ the Lord who, during his life on earth, offered up prayers and supplications to God with loud cries and tears, and now sits at the right hand of the divine majesty, always living to make intercession for us (Heb. 5:7, 1:3, 7:25). They should also remember the the exhortations of the Apostle: "Pray without ceasing" (I Thes. 5:17); "Be filled with the Holy Spirit, addressing one another in psalms and hymns and spiritual songs" (Eph. 5:19); "First of all I urge that petitions, prayers, intercessions and thanksgiving be offered for all" (1 Tim. 2:1). From the Constitutions of the Nuns of the Order of Preachers
"Imitating blessed Dominic as he imitated Christ (cf. I Cor. 4:16), they should perpetuate his "fervor and spirit of prayer" for "he celebrated the whole Divine Office with great devotion"; 'was tireless in prayer'; 'during the night hours, no one was more constant in every way in prayer and vigils'; frequently 'he prayed to his Father with his door closed.' Nor should they forget his cry: 'Lord, what will become of sinners?' Therefore, the whole life of the nuns is harmoniously ordered to preserving the continual remembrance of God. By the celebration of the Eucharist and the Divine Office, by reading and meditating on the Sacred Scriptures, by private prayer, vigils and intercessions they should strive to have the same mind as Christ Jesus. In silence and stillness, let them earnestly seek the face of the Lord and never cease making intercession with the God of our salvation that all men and women might be saved. They should give thanks to God the Father who has called them out of darkness into his wonderful light. Let Christ, who was fastened to the cross for all, be fast-knit to their hearts. In fulfilling all these things, they are truly nuns of the Order of Preachers." From the Constitutions of the Nuns of the Order of Preachers
"In the liturgy the mystery of salvation is present and at work, especially in the Eucharist, in which Christ is received, the memory of his passion is recalled, the soul is filled with grace and a pledge of future glory is given. Appointed for the work of divine praise, the nuns, in union with Christ, glorify God for the eternal purpose of his will and the marvelous dispensation of grace. They intercede with the Father of mercies for the universal Church as well as for the needs and salvation of the whole world. This joyful celebration joins the pilgrim Church to the Church in glory. Hence the solemn celebration of the liturgy is the heart of our whole life and the chief source of its unity. The conventual Mass should be the center of the community liturgy. As a memorial of the death and resurrection of the Lord, it is the bond of fraternal charity and the primary source of apostolic zeal."
From the Constitutions of the Nuns of the Order of Preachers