Jeremiah stands before the people, delivering a stark warning about the consequences of silencing a prophet. He makes it clear that executing him will not prevent the impending disaster he has foretold. Instead of saving the nation, taking his life will only worsen their situation and add to their sins.
The prophet cautions that the burden of innocent blood will fall upon them. Commentators agree that this is not meant literally, but rather represents the profound guilt and blame the people will carry for murdering a blameless man [מצודת דוד, ביאור שטיינזלץ]. By committing this act, the people will fail to remove the threat hanging over them. On the contrary, they will only draw the anger of God down upon themselves and upon the city of Jerusalem [ביאור שטיינזלץ, מלבי״ם]. Executing him would be a terrible injustice, because he is not speaking on his own authority; he is acting as a true and faithful messenger sent directly by God [מלבי״ם].