The order of events in the original Hebrew text is different from that in many translations. The first items mentioned are the murder weapons: the war club, the sword, and the sharp arrow. This immediately shows how life-threatening the situation is, raising the uneasy question: What makes this so threatening? The answer is found in the second part of the saying: Someone bears false witness against his neighbour. Doing something like this can indeed lead to death.
The words that are being used here are the same as in the ninth commandment that the nation of Israel once heard (in Exodus 20:16; Deuteronomy 5:20). The Lord strictly warns us here against bearing false witness against a neighbour. Whoever does that goes against the order that God has put in place. Therefore, know what you are doing!
Realize well that your false witness can even cause the death of someone else (see 1 Kings 21:1–29).
18 A man who bears false witness against his neighbor is like a war club, or a sword, or a sharp arrow.