The Gospel text is one that would likely be fairly familiar to most people in this congregation. Aside from the fact that they would have heard it the last time around in the lectionary, there is the language used in just about every baptism here: "Let your light so shine..."
The Gospel also has the idea of salt and saltiness--a natural springboard for talking about Spiritual Gifts. Then there is the overt mentioning of Law and Gospel, a Lutheran standard. Going a little into the details of that one, the mentioning of the letters and strokes of the letters of the law in verse 18 likely refers to the jot and tittle (yodh being the smallest letter and tittles being the distinguishing marks for the letters of the Hebrew alef bet).
Corinthians proclaims the fact that we cannot know anything on our own, which is simliar to Luther's statement on the third article of the Apostles' Creed found in the Small Catechism:
"I believe that by my own understanding or strength I cannot believe in Jesus
Christ my Lord or come to him, but instead the Holy Spirit has called me through
the gospel, enlightened me with [gifts], made me holy, and kept me in the true
Isaiah and the Psalm are also intriguing in that they talk a great deal about justice and righteousness as those who give of themselves and their possessions to those in need of them. Stewardship would be easily addressed through these texts--stewardship of our whole selves, not just our finances.
Essentially, these texts hold many possibilities--catechism, baptism, stewardship, Law/Gospel, gifts of the Spirit, social justice. I look forward to seeing what the commentaries have to say.