Linus is right.
3 seconds sound clip from the A Charlie Brown Christmas movie soundboard.
You can hear this line at 00:22:35 in the Blu-ray version of the movie.
Quote context
[...]
- And suddenly, there was with the angel a multitude of the heavenly host praising God and saying...
- 'Glory to God in the highest, and on Earth, peace, goodwill toward men.'
- That's what Christmas is all about, Charlie Brown.
- For, behold, I bring you tidings of great joy which shall be to all people.
- I won't let all this commercialism ruin my Christmas.
- I'll take this little tree home and decorate it, and I'll show them it really will work in our play.
- Oh, well. This commercial dog is not going to ruin my Christmas.
[...]