Your nose will glow, so long as you use it for good. If you are tempted, even once, to use it for an evil purpose, it will be extinguished forever.
16 seconds sound clip from the Rudolph and Frosty: Christmas in July movie soundboard.
You can hear this line at 00:13:04 in the Blu-ray version of the movie.
Quote context
[...]
- Little one, I have so little magic left to leave thee. Use it wisely and well.
- On this small hoof, a magic mark I make. The Christmas star, cradled by a snowflake.
- And with this secret mark, the magic of the northern lights lives in thee.
- How, you ask? Think good thoughts and you will see.
- Do you understand? And will you never use it for evil?
- And now I leave you, little babe, to your mother's love.
- Oh! What was that? Was someone here?
- Can't you make up your mind, my little one?
[...]