Wizard has it spot on I reckon.
It is probably best understood by reading Psalm 7.
David knows that God is the ultimate universal judge of human affairs and this brings him great comfort. However, David also notices that this does not bode well for the wicked* so he instructs them regarding impending judgment. The imagery of the sharpened sword and bent bow indicate both God�s longsuffering and the inevitability of judgment. God is poised and ready to bring wrath, but there is still time to repent, whether in the OT or NT and thus God will provide justice, sanctuary and protection. Look up �doctrine of the two swords� for more.
* of bad nature or condition, human or spiritual (the essence of sin).