Their feet are swift to shed blood:

People's New Testament

3:15 Their feet are swift to shed blood. To carry their owners on a mission of murder.

Wesley's Notes

3:15 Isaiah 59:7,8

Jamieson-Fausset-Brown Bible Commentary

15. Their feet are swift to shed blood-(Pr 1:16; Isa 59:7): that is, "Those feet, which should 'run the way of God's commandments' (Ps 119:32), are employed to conduct men to deeds of darkest crime."

Matthew Henry's Concise Commentary

3:9-18 Here again is shown that all mankind are under the guilt of sin, as a burden; and under the government and dominion of sin, as enslaved to it, to work wickedness. This is made plain by several passages of Scripture from the Old Testament, which describe the corrupt and depraved state of all men, till grace restrain or change them. Great as our advantages are, these texts describe multitudes who call themselves Christians. Their principles and conduct prove that there is no fear of God before their eyes. And where no fear of God is, no good is to be looked for.