Here "by the hand" is an idiom that means to be the specific cause of something. Alternate translation: "would not be killed by the avenger" (See: [[rc://en/ta/man/jit/figs-idiom]])
This was a relative of the person who had been killed. His job was to kill the person who had killed his relative.
# blood
Blood is a metonym for the death of the person whose blood has been shed. See how you translated this in [Joshua 20:3](../20/03.md). Alternate translation: "death" (See: [[rc://en/ta/man/jit/figs-metonymy]])