Here's how it appears in Christmas Carols, Ancient and Modern by William Sandys (London: Richard Beckley, 1833), page 102. Note there are several differences from how we sing it today. In particular, notice the second line of the refrain. It would be very awkward to fit that to the tune I know. Unfortunately, the book doesn't give a tune.

I have boldfaced the differences. For the verses that haven't been posted at Mudcat before, I use the version in the NetHymnal (formerly known as CyberHymnal) for comparison.


GOD REST YOU MERRY, GENTLEMEN.

1. God rest you merry, gentlemen, let nothing you dismay,
For Jesus Christ our Saviour was born upon this day,
To save us all from Satan's power when we were gone astray.
    O tidings of comfort and joy,
    For Jesus Christ our Saviour was born on Christmas day.

2. In Bethlehem in Jury [=Jewry] this blessed babe was born,
And laid within a manger upon this blessed morn;
The which his mother Mary nothing did take in scorn.
    O tidings, &c.

3. From God our Heavenly Father a blessed Angel came,
And unto certain Shepherds brought tidings of the same,
How that in Bethlehem was born The Son of God by name.
    O tidings, &c.

4. Fear not, then said the Angel, Let nothing you affright,
This day is born a Saviour of virtue, power, and might;
So frequently to vanquish all the friends of Satan quite.
    O tidings, &c.

5. The Shepherds at those tidings rejoiced much in mind,
And left their flocks a feeding in tempest, storm, and wind,
And went to Bethlehem straightway, this blessed babe to find.
    O tidings, &c.

6. But when to Bethlehem they came, whereas this infant lay,
They found him in a manger where oxen feed on hay,
His mother Mary kneeling unto the Lord did pray.
    O tidings, &c.

7. Now to the Lord sing praises, all you within this place,
And with true love and brotherhood each other now embrace;
This holy tide of Christmas all others doth deface.
    O tidings, &c.