Paul speaks of God's message as if it were a person who can move. The word "mouth" is a metonym that refers to what a person says. The phrase "in your heart" is metonym that refers to what a person thinks and believes. Alternate translation: "You have heard the message. You know how to speak it, and you know what it means" (See: [[rc://en/ta/man/jit/figs-personification]] and [[rc://en/ta/man/jit/figs-metonymy]])