| Barnes' Notes on the Bible Their feet ... - The quotation in this and the two following verses, is abridged or condensed from Isaiah 59:7-8. The expressions occur in the midst of a description of the character of the nation in the time of the prophet. The apostle has selected a few expressions out of many, rather making a reference to the entire passage, than a formal quotation. The expression, "their feet are swift," etc., denotes the eagerness of the nation to commit crime, particularly deeds of injustice and cruelty. They thirsted for the blood of innocence, and hasted to shed it, to gratify their malice, or to satisfy their vengeance.
Clarke's Commentary on the BibleTheir feet are swift to shed blood - They make use of every means in their power to destroy the reputation and lives of the innocent.
Gill's Exposition of the Entire BibleTheir feet are swift to shed blood. The sins of the heart and mouth are before described, and now the sins of action are taken notice of; for "the feet" are the instruments of motion and action: and when these are said to be "swift to shed blood", it denotes the readiness and eagerness of men, to murder innocent creatures; which shows the dreadful malice and hatred that is in them. The words are cited from Isaiah 59:7, and seem to point at the times of Manasseh, who shed so much innocent blood, as to fill Jerusalem with it from one end to the other.
Geneva Study BibleTheir 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 Commentary15. 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 Commentary3:9-18 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. | 
