Bell, book and candle is a phrase from the Roman Catholic ritual for excommunication that sometimes is used to denote a witch or witchcraft. Excommunication, or exclusion from the religious fellowship of the church, represents a condemnation to spiritual darkness, with repercussions in society. The excommunicated becomes an outcast in secular as well as religious life.
The rite is the equivalent of a Curse and involves a bell, the holy Book and a candle or candles. The priest reads the following sentence:
We exclude him from the bosom of our Holy Mother the Church, and we judge him condemned to eternal fire with Satan and his angels and all the reprobate, so long as he will not burst the fetters of the Demon, do penance and satisfy the Church.
The priest then closes the book, rings a bell — a symbolic toll for death — extinguishes the candle and throws it down, which symbolizes the removal of the victim's soul from the sight of God.
The phrase “bell, book and candle” became associated with witches because the church believed them to be Devil-worshippers who should be excommunicated.