Binding spell

The Binding Spell is a spell used on witches to prevent them from using magic for bad intent or at all. The spell is used by wrapping a white ribbon around a picture of someone whose powers you wish to bind.

Method
The official method in the movie is to take a picture of the witch whose powers you wish to bind, wrap a white ribbon around it and then chant the following:

"I bind you, [Person's Name], from doing harm; harm against other people, and harm against yourself."

If all goes well, then the named witch will lose the ability to use magic, rendering them powerless. It is possible, however, for the spell to fail. It is also shown to be possible for a witch of substantial power to bind a witch with just the verbal spell.

The Craft
The spell was first used by Sarah against Nancy when she realized that the power Nancy had inherited from Manon was turning her evil. The spell initially never worked and Nancy figured out she used the spell on her.

The spell was secondly used after Sarah used the invocation of the spirit ritual against Nancy again to keep her from doing harm to others. This time Sarah took away powers completely from Nancy, along with Rochelle and Bonnie.

Trivia

 * It is not specified if the binding spell always results in permanent loss of magic, or if the spell can be removed or reworked to have only a temporary effect.
 * It is unclear what effect the spell may have on a natural witch, given they are in fact born with their powers.