Ministers and other people from Christian traditions that do not use pre-appointed lectionary readings often think that the use of lectionaries greatly limits the topics that can be preached on. This would especially seem to be the case with the 1928 BCP eucharististic lectionary, which runs on a one-year cycle. The modern solution, of course, was to adopt a three-year lectionary, to give the preacher more options and bring more of the bible into the liturgy. Some continuing parishes use the three-year lectionary, but most still use the old one. Either way, if the readings are pre-appointed, it can seem somewhat limiting on the surface. So what do you do? You have to get creative.
I find it very easy to do "topical" sermons based on the lectionary. A few weeks back we had the John 9 as our Gospel, so I chose to preach on the concept of "light" and how Christ is the light of the world. Two weeks ago, when the Gospel was about the doubting St. Thomas I preached on "inner peace". ("Peace be with you.") So I don't know what other priests do, but I will often pull out one word or verse and build off of that. I always try to relate the concept to the liturgy of the Church and the Eucharist, showing, for example, how many times we use "peace" in the liturgy. One thing that sermons should always do is point to redemption in Jesus Christ, and especially in the Holy Eucharist (I learned that from a Dominican sister in seminary). Related to that, I find that one can never mention the Holy Name too much in a sermon. His very name is immeasurably powerful and needs to be spoken aloud. Topical sermons can also be done based on the theme of the Sunday (e.g. "Good Shepherd" Sunday), or where we are in the Church year and what the feast day is. But the point is that with a little bit of creativity it is possible to speak on any number of topics and themes based on pre-appointed lectionary readings. Other times, of course, it is appropriate to try to exegete the entire passage and discuss the broad theme of the entire reading. I do not want to deny the importance of that, but it can become rather limiting after a while.
