Charmed, the Book of Shadows

 "In Charmed, the “Book of Shadows” is actually the Halliwell sisters’ book, but it is filled with anti-demonic spells. If you remember the scene where the sisters burn a spell in it, this detail is tied to episodes where they have to undo, destroy, or “unfreeze” a dangerous spell.

However, throughout the series, there is no specific spell that is referred to as “a spell burned from the Book of Shadows”. Common scenes include:

They erase, edit, or create new spells in the Book of Shadows to adapt to new threats.

When destroying dark entities (like The Source or warlocks), they often use fire to destroy the associated spell, but the show does not specify a “single spell”.

 So if you're thinking of the burning of a spell, it's probably more of a symbolic moment than a specific spell—it represents the Halliwell sisters personally erasing some of the power of darkness to assert the power of light."