27 Therefore, We exhort the priests to provide that their own knowledge of things Divine and human be wide and deep; that they be not content with the intellectual knowledge acquired in youth; that they examine with careful scrutiny the Law of the Lord, Whose oracles are purer than silver; that they continually relish and enjoy the chaste charms of Sacred Scripture; that with the passing of the years they study more deeply the history of the Church, its dogmas, its Sacraments, its laws, its scriptures, its liturgy, its language, so that they may advance in grace, in culture and wisdom.
Source: Sertum Laetitiae (Vatican.va)