(The following questions are from my basic method on Law and Gospel preaching. The entire method is laid out in my book, Afflicting the Comfortable, Comforting the Afflicted. These questions try to get at some of the foundational questions for Law and Gospel preachers.)
1. How does the Word function in the text? The Word, Jesus, both promises and rebukes in this text. In this way, the Word is functioning as both law and gospel. By saying to his listeners, "Your ancestors ate the manna in the wilderness, and they died," Jesus is reminding his listeners that "the food that perishes" (vs.27) will never sustain them. He is reminding them of their need for Himself, the bread come down from heaven. By announcing that "I am the living bread that came down from heaven. Whoever eats of this bread will live forever," Jesus is giving them Himself. He is proclaiming gospel. These two functions - to point to the inadequacies of perishable 'bread', and to point to the adequacy of Christ - will be our two main tasks in the sermon.
2. How is the Word not functioning in the text? The third function of the Word in a text is the call to obedience - a word that says, "Follow me." There is no such word here. Jesus is calling us to faith, but beyond that we have no guidance. There are many other texts we can use that will help us with this, notably the second lesson appointed for the day - Ephesians 4:25-32 - which speaks about building up one another. One strategy we can employ might be to announce how Christ feeds us - builds us up - and in turn, we are called to build up others.
3. With whom are you identifying in the text? It is very important to identify with the Jews in the text - those that are offended by Jesus' word. This text gives us a good chance to ponder how offensive Jesus' words are to us at times, and to consider how we, as preachers, might risk offending our listeners in order to bring them the bread of life.
4. What Law/Gospel couplet is suggested by this text? Some of the same ones we have used earlier in this 'bread' series will do: hungry/fed, thirsty/satisfied. We might also think about other couplets such as complaining/ believing, manna/bread of heaven, dying/eternal life.
5. Exegetical insights: I find Raymond Brown's classic commentary, The Gospel According to John I-XII, very helpful with this text. Brown points out that the word translated "complain" in verse 41 is the same word as the Septuagint uses for the murmuring of the Israelites in Exodus 14. This is a hint that John is drawing on ancient story and memory here in speaking of murmuring, manna, and bread from heaven. These people, who resist Jesus, are God's people. They are like the Israelites of old, pushing back against God's demands and God's provision. Any study we do of the stories of the Israelites' murmurings and wanderings in the wilderness will likely bear much fruit in unearthing the meaning of John's artful language in this text.
6. How does the Crossings Community model work with this text? Bill White has written an excellent example of the model for this text archived at crossings.org/text study under 2012 Year B Gospel for the 11th Sunday after Pentecost. I recommend taking a look at it.
Blessings on your proclamation!