Matthew summarizes Jesus’ opening message as: "Repent, for the kingdom of heaven is at hand" Matthew 4:17. This begins after Jesus starts ministering in Galilee Matthew 4:12.
In Matthew 4:17 Jesus’ public message is introduced in one sentence. This verse functions like a hinge in Matthew’s story. After Jesus’ preparation narrative (his baptism and testing) and after the report of his move into Galilee, Matthew marks a new phase: “From that time” signals that Jesus’ main public activity now begins.
Matthew presents this line as the launch of Jesus’ public message. It is a repeated slogan-like summary (“began to preach and to say”), not a private conversation.
A careful answer keeps the immediate passage, the book's argument, and the whole-Bible storyline together, so the question is answered in context instead of as a detached idea.
Start with Matthew 4:17, then read the surrounding section so the answer stays connected to the passage's flow.
17From that time, Jesus began to preach, and to say, "Repent! For the Kingdom of Heaven is at hand."