The sermon or homily is not a lengthy dissertation. It is not a teaching on philosophy. It is not an impartation of factual statements about the faith. Rather, it should use an economy of words similar to a poem. Much can be expressed in poetry. The poet can express deep meaning without spelling out great detail.
This, of course, requires the listener to do some work. Through careful reflection, the listener must be engaged and open to what the homilist might be saying. The beauty of the poetic preaching will catch many listeners.
The Gospel of John is very poetic. It has the simplest vocabulary of all the Gospels. Yet the Gospel of John is very deep with meaning. Each time it is read it is able to convey new levels of understanding. How does this happen? The Holy Spirit continues to breath new meaning through this Gospel.
The homilist does not to deliberately write a poetic homily. Rather, when the homilist is open to the Holy Spirit, allowing the Spirit to have a major role in shaping and phrasing the text of the homily, the Spirit will do the poetry. Different listeners may hear different messages which might seem specific to each one of them. This is how a sermon or homily behaves as a poem.