In the Old Testament Ezekiel prophesied the words that the Lord caused him to eat. "'Son of man, eat this scroll, and go, speak to the house of Israel.' So I opened my mouth, and He caused me to eat that scroll" (Ezekiel 3:1-2).
Therefore, I don't take it to be mere factual reporting when the Scriptures speak of John the Baptist's diet. "His food was locusts and wild honey" (Matthew 3:4). John preached what he ate. Locusts portray condemnation and the judgment of God, as in the book of Joel. John preached this Law sternly. "Repent! Brood of vipers! Who warned you to flee from the wrath to come? Bear fruits worthy of repentance." But then He also preached the Gospel in all its sweetness, like honey in His mouth. "The kingdom of heaven is at hand. Behold the Lamb of God who takes away the sins of the world!" This Law and Gospel is still the content of all true Christian preaching. "How sweet are your words to my taste, sweeter than honey to my mouth" (Psalm 119:103).
You proclaim what you eat. Is this not what is meant when the Scriptures speak of Christians prophesying? We proclaim the praises of Him whom we eat in the Sacrament, that is, we confess the Christ whose body was sacrificed on our behalf and whose blood was shed to cleanse us of our sins. "For as often as you eat this bread and drink this cup, you proclaim the Lord's death till He comes" (1 Corinthians 11:26).