Albert Barnes Commentary Psalms 94:21

"They gather themselves together against the soul of the righteous, And condemn the innocent blood." — Psalms 94:21 (ASV)

They gather themselves together against the soul of the righteous - Against the life of the righteous; that is, to take their lives. The Hebrew word rendered “gather together,” means to press or crowd upon anyone; to rush in crowds or troops. It would refer particularly to a tumultuous gathering - “a mob” - intent on accomplishing its purpose.

And condemn the innocent blood - literally, make guilty; that is, they hold that blood to be guilty; or, they treat the innocent as if they were guilty.