§1. A diocesan bishop, frequently preaching in person, is bound to propose and explain to the faithful the truths of the faith which are to be believed and applied to morals. He is also to take care that the prescripts of the canons on the ministry of the word, especially those on the homily and catechetical instruction, are carefully observed so that the whole Christian doctrine is handed on to all.
§2. Through more suitable means, he is firmly to protect the integrity and unity of the faith to be believed, while nonetheless acknowledging a just freedom in further investigating its truths.
Source: Code of Canon Law (Vatican.va)