When would it make sense to select Isaiah 9:1-7 as your sermon text?
This text could be preached as part of a series of sermons during Advent.
If you use the lectionary, Isaiah 9:2-7 is the Old Testament reading for Christmas Eve. Isaiah 9:1-4 is the Old Testament reading for the third week after Epiphany in Year A.
If you are a pastor in the Dutch Reformed tradition, and your text selection is guided by the content of the Heidelberg Catechism, Isaiah 9:1-7 could be preached in connection with Answer 31, where the Catechism is dealing with the name “Christ” in the Apostles’ Creed. The Catechism says that Christ has been anointed with the Holy Spirit “to be our eternal king, who governs us by his Word and Spirit, and who guards us and keeps us in the freedom he has won for us.”[1]
On the question of what the limits of the text should be, see the review of where the text begins and ends in Isaiah 9:1-7 – Step Two.