Personal Gain

Paige is "busted" for using her powers for personal gain

Personal gain is the term applied when a good magical being (such as a witch) uses his or her powers for his or her own profit. Magical beings that do so risk suffering certain consequences; ranging from simply losing any benefit gained to someone being killed. Hence, when spells are cast for personal gain, they could backfire.

The Wiccan Rede

"And it harm none, do what you will."

The Wiccan Rede is the most basic yet fundamental of magical rules, which establishes that good witches cannot use their powers for their own personal gain, including beauty and love spells. They are also not allowed to use magic for punishment purposes even if the person is truly guilty of an offense, for good witches are only supposed to "protect the innocent, not punish the guilty."

If a witch goes against the Wiccan Rede, he or she will have to face consequences: he or she would have to either suffer punishment, or the magic that he or she had used would backfire on him or her. An example of this could be seen when Paige used magic to punish a man who had a habit of making sexist comments, but it resulted in her having engorged breasts.

It is also possible for witches to not suffer from any negative consequences, but instead, any benefits from their acts of personal gain would be negated. An example of this could be seen when Phoebe tries to win the lottery after having a premonition of the results, only for the corresponding numbers to disappear from the ticket when results are broadcasted.

Since evil is already in violation of the Wiccan Rede and therefore not bound by any issues of morality, it is not limited by personal gain and could use magic however it desired. Phoebe herself pointed that this was what made evil so tempting - the sensation of being able to do whatever they wanted whenever they wanted, without the voice of a conscience holding them back with reminders of morality and the potential consequences that could stem from their actions. However, Paige also pointed out that this was what separated Good from Evil.

Neutral Beings

Personal Gain also poses a threat to neutral beings such as the Avatars. Alpha attempted to dissuade Cole Turner when he used his new powers to create a alternate reality in a last ditch to get Phoebe back. In this reality he never got sent to the demonic wasteland, thus becoming vulnerable and finally being vanquished. When Leo became an Avatar, he used the power of Chronokinesis unintentionally and was warned by Alpha not do so again. However, personal gain for Avatars is strongly discouraged because it weakens the collective magical power rather than a rule itself.

Mortals Gain Magic

The result of mortals using magic

After the Darklighter Rennek used stolen magical knowledge from Leo, he caused magic to switch sides to all beings that were on Earth at the moment. Because of this, mortals gained the ability to use magic.

With the Earth cut off from the Elders, the Angels of Destiny and all forms of authority, mortals used magic for their personal gain such as magically altering their houses without regard. Piper believed that there would be repercussions, though it is not known if personal gain applies to mortals, as they are technically a neutral party.

When magic was restored to magical beings and mortals became powerless again, Prue Halliwell cast a memory-wipe spell to ensure magic was not exposed, though also ensured that the mortals would never fully forget either.

Notes and Trivia

• The rules of personal gain were featured more in earlier seasons than in the latter, where the sisters started using magic more casually and it often went unpunished. Some cases could be viewed as bordering on harming mortals, such as Phoebe using a potion to turning a rival advice columnist into an animal on more than one occasion. A notable exception is "Crimes and Witch-Demeanors", where Phoebe Halliwell loses her powers after using them extensively for personal gain. 
• There are small instances of personal gain throughout the series with no punishment to follow up, mostly in the form of Piper freezing annoyances or Prue (and later Paige) telekinetically moving objects in order to complete mundane tasks. They might not have warranted any consequences since they were only minor offenses with little benefit.
• In "Piper's Place", Wyatt uses the Charm of Multiplicity to create several Pipers. More clones appear as time passes until Wyatt reverses the spell. This is presumably a side effect of personal gain, or Wyatt overloading the spell with his magic.