Who said "The most powerful spell is one cast with pure intention."?

This quote is attributed to Albus Dumbledore.

The most powerful spell is one cast with pure intention. - Albus Dumbledore

"The most powerful spell is one cast with pure intention."

Albus Dumbledore

"It is our choices that show what we truly are, far more than our abilities."

"The truth is a beautiful and terrible thing, and should therefore be treated with great caution."

"Happiness can be found even in the darkest of times, if one only remembers to look for it."

"It takes a great deal of bravery to stand up to our enemies, but just as much to stand up to our friends."