Sacerdotii Nostri Primordia §44

⁴⁴ To use the words of St. Pius X: "We are sure of this much... that a priest must be deeply devoted to the practice of prayer if he is to live up to his rank and fulfill his duties properly... For a priest must be much more careful than others to obey the command of Christ: You must always pray. Paul was only reaffirming this when he advised, as he did so often: Be constant in prayer, ever on the watch to give thanks; pray without ceasing." (57) And We are more than happy to adopt as Our own the words that Our immediate predecessor offered priests as their password at the very beginning of his pontificate: "Pray, more and more, and pray more intensely." (58)