I generally use the Revised Common Lectionary when I preach. The lectionary is a set of readings for use in the service on Sunday. It is on a three year cycle, and each day has an Old Testament reading, a Psalm, a reading from the Gospels, and a reading from the rest of the New Testament. Lectionary use is fairly rare in my tradition, but I think that it has two advantages. First, there is the comfort of knowing that other churches around the world are using the same texts on that same day. Second, I am forced to preach on passages that I otherwise probably wouldn't consider.
The problem with using the lectionary is the challenge of finding a way to make a particular text that you did not choose relevant for your congregation on that day. Most of the time, it's very easy, but it can be difficult sometimes. This week, when I opened my Bible to the Psalm for the week, Psalm 137, I knew that relevance would not be a problem:
"By the rivers of Babylon— there we sat down and there we wept when we remembered Zion. On the willows there we hung up our harps. For there our captors asked us for songs, and our tormentors asked for mirth, saying, 'Sing us one of the songs of Zion!' How could we sing the Lord’s song in a foreign land?" (Psalm 137:1-4, NRSV)
I took a trip to give some briefings to soldiers who are going home. We flew for quite a while over the Tigris river while I pondered being by the rivers of Babylon. I could always hear the pain in the Psalmist's voice as I read it in the past. Now, though, I understand it in ways that I never have before.