It's a song written by John Lennon and Yoko Ono and released in 1971. This song was a protest song about the Vietnam War, it has become a Christmas standard. The recording starts with spoken Christmas greetings from Ono and Lennon to their children: Ono whispers "Happy Christmas, Kyoto", then Lennon whispers "Happy Christmas, Julian".

So this is Christmas
And what have you done
Another year over
And a new one just begun
And so this is Christmas
I hope you have fun
The near and the dear one
The old and the young

A very Merry Christmas
And a happy New Year
Let's hope it's a good one
Without any fear

And so this is Christmas
For weak and for strong
For rich and the poor ones
The world is so wrong

And so happy Christmas
For black and for white
For yellow and red ones
Let's stop all the fight

A very Merry Christmas
And a happy New Year
Let's hope it's a good one
Without any fear

And so this is Christmas
And what have we done
Another year over
A new one just begun

And so happy Christmas
We hope you have fun
The near and the dear one
The old and the young
A very Merry Christmas
And a happy New Year
Let's hope it's a good one
Without any fear

War is over, if you want it
War is over now

Happy Christmas.