The blessing makes these candles into “sacramentals,” an extension of the sacraments of the Church and a channel of divine grace.
One spiritual benefit of blessed candles is their ability to drive out the demonic. This is clearly shown in the blessing found in the Roman Ritual.
Lord Jesus Christ, Son of the living God, bless + these candles at our lowly request. Endow them, Lord, by the power of the holy + cross, with a blessing from on high, you who gave them to mankind in order to dispel darkness. Let the blessing that they receive from the sign of the holy + cross be so effectual that, wherever they are lighted or placed, the princes of darkness may depart in trembling from all these places, and flee in fear, along with all their legions, and never more dare to disturb or molest those who serve you, the almighty God, who live and reign forever and ever.
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