14 “And in it He has prepared the instruments of death: He has wrought His arrows for the burning”. That bow then I would readily take to be the Holy Scripture, in which by the strength of the New Testament, as by a sort of string, the hardness of the Old has been bent and subdued. From thence the Apostles are sent forth like arrows, or divine preachings are shot. Which arrows “He has wrought for the burning,” arrows, that is, whereby being stricken they might be inflamed with heavenly love.
For by what other arrows was she stricken, who says, “Bring me into the house of wine, place me among perfumes, crowd me among honey, for I have been wounded with love”? By what other arrows is he kindled, who, desirous of returning to God, and coming back from wandering, asks for help against crafty tongues, and to whom it is said, “What shall be given you, or what added to you against the crafty tongue? Sharp arrows of the mighty, with devastating coals:” that is, coals, whereby, when you are stricken and set on fire, you may burn with so great love of the kingdom of heaven, as to despise the tongues of all that resist you, and would recall you from your purpose, and to deride their persecutions, saying, “Who shall separate me from the love of Christ?
Shall tribulation, or distress, or persecution, or famine, or nakedness, or peril, or sword? For I am persuaded,” he says, “that neither death, nor life, nor angel, nor principality, nor things present, not things to come, nor power, nor height, nor depth, nor other creature, shall be able to separate me from the love of God, which is in Christ Jesus our Lord.” Thus for the burning has He wrought His arrows. For in the Greek copies it is found thus, “He has wrought His arrows for the burning.” But most of the Latin copies have “burning arrows.” But whether the arrows themselves burn, or make others burn, which of course they cannot do unless they burn themselves, the sense is complete.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)