The song was written by Irving Berlin the same year as it's original release in 1942. It debuted in the movie, Holiday Inn, and was later used in a film that was made due to the popularity of the song. Naturally, that movie was called, White Christmas.
Here's a link to the original recording on YouTube. If you'd like to sing along, the lyrics are below.
Click to listen - Bing Crosby - White Christmas - 1942 original version- 78RPM
I'm dreaming of a white Christmas
Just like the ones I used to know
Where the treetops glisten,
and children listen
To hear sleigh bells in the snow
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I'm dreaming of a white Christmas
With every Christmas card I write
May your days be merry and bright
And may all your Christmases be white
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I'm dreaming of a white Christmas
With every Christmas card I write
May your days be merry and bright
And may all your Christmases be white
~~~~~~~~~~~~~~~~~~~ Enjoy! ~~~~~~~~~~~~~~~~~~