Adam Clarke on Psalms 94:1

O Lord God, to whom vengeance belongeth - God is the author of retributive justice, as well as of mercy. This retributive justice is what we often term vengeance, but perhaps improperly; for vengeance with us signifies an excitement of angry passions, in order to gratify a vindictive spirit, which supposes itself to have received some real injury; whereas what is here referred to is that simple act of justice which gives to all their due.