Thomas Aquinas

Then when he says their feet swift he touches on sinful deeds, in regard to which he mentions three things. First, readiness to do wickedly. Hence he says, their feet swift, i.e., their feelings, to shed blood, i.e., to commit any serious sin, because among the sins committed against our neighbor, murder is the most grievous: their feet run to evil, and they make haste to shed blood (Prov 1:16).

Commentary on Romans ↗