Translation, God is saying "watch your mouth" because many Christian's are actually becoming accessories to murder; spiritual murder.
How? By participating in a "fire mission" launched by the Devil! Devil comes from the Greek word diablos and means false accuser or slanderer. Today, many Christians are slipping up and becoming part of the character assassination fire missions initiated by our adversary. In doing so you become an accessory to a spiritual crime.
What Does Accessory Mean?
Wikipedia says accessory is a legal term for "a person who assists in the commission of a crime, but who does not actually participate in the commission of the crime as a joint principal. The principal is the one whose acts or omissions, accompanied by the relevant mens rea (Latin for "guilty mind"), are the most immediate cause of the actus reus (Latin for "guilty act").".... The test to distinguish a joint principal from an accessory is whether the defendant independently contributed to causing the actus reus rather than merely giving generalized and/or limited help and encouragement."
So an accessory is someone who gives generalized or limited help and encouragement.
You may not be the originator, the instigator, nor the deceiver who developed the lie but when we join in by repeating that lie, we become an accessory to murder. We either kill the truth or we participate in the fire mission intent on the character assassination of another.
The Trump Presidency Provides a Modern Example