Canon 767. §1 The most important form of preaching is the homily, which is part of the liturgy, and is reserved to a priest or deacon. In the course of the liturgical year, the mysteries of faith and the rules of christian living are to be expounded in the homily from the sacred text.
[NB see Authentic Interpretation of canon 767 §1, 20.VI.1987]

§2 At all Masses on Sundays and holydays of obligation, celebrated with a congregation, there is to be a homily and, except for a grave reason, this may not be omitted.

§3 It is strongly recommended that, if a sufficient number of people are present, there be a homily at weekday Masses also, especially during Advent and Lent, or on a feast day or an occasion of grief.

§4 It is the responsibility of the parish priest or the rector of a church to ensure that these provisions are carefully observed.

§1. Inter praedicationis formas eminet homilia, quae est pars ipsius liturgiae et sacerdoti aut diacono reservatur; in eadem per anni liturgici cursum ex textu sacro fidei mysteria et normae vitae christianae exponantur.

§2. In omnibus Missis diebus dominicis et festis de praecepto, quae concursu populi celebrantur, homilia habenda est nec omitti potest nisi gravi de causa.

§3. Valde commendatur ut, si sufficiens detur populi concursus, homilia habeatur etiam in Missis quae infra hebdomadam, praesertim tempore adventus et quadragesimae aut occasione alicuius festi vel luctuosi eventus, celebrentur.

§4. Parochi aut ecclesiae rectoris est curare ut haec praescripta religiose serventur.