Charles Ellicott 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 — that is, possibly, They crowd into the courts of law to take part in the unjust condemnation of the just, or more generally, “They attack the life of the righteous.” Septuagint, “they hunt.” .