Blessing a weapon of God

Richard Barbers book "The Knight and Chivalry" explains how the one way of investiture was to place the knights sword on the alter during mass and with following prayer said over it:

“Hearken, we beseech thee, O Lord, to our prayers, and deign to bless with the right hand of thy majesty this sword with which this Thy servant desires to be girded, that it may be a defense of churches, widows, orphans and all thy servants against the scourge of the pagans, that it may be the terror and dread of other evildoers, and that it may be just both in attack and defense.”

Flori, Essor de la Chevalerie, 90-2 for discussion; text, 379.