Hymn Study: While shepherds watched their flocks by night

 This Hymn is based on this Scripture passage.
 

⁸ And in the same region there were shepherds out in the field, keeping watch over their flock by night. ⁹ And an angel of the Lord appeared to them, and the glory of the Lord shone around them, and they were filled with great fear. ¹⁰ And the angel said to them, “Fear not, for behold, I bring you good news of great joy that will be for all the people. ¹¹ For unto you is born this day in the city of David a Savior, who is Christ the Lord. ¹² And this will be a sign for you: you will find a baby wrapped in swaddling cloths and lying in a manger.” ¹³ And suddenly there was with the angel a multitude of the heavenly host praising God and saying,

¹⁴ “Glory to God in the highest,
    and on earth peace among those with whom he is pleased!”   Luke 2:8-14

This hymn is attributed to England Poet Laureate Natum Tate.    Until 1782, it was the only Christmas carol officially sanctioned by the Church of England.  (source) All others hymns were taken from the Psalms.

Natum Tate and Nicholas Brady collaborated on a Psalter entitled New Version of the Psalms of David, which they published in 1696 to replace an earlier Psalter that had been published by Thomas Sternhold and John Hopkins in 1562.  The Psalter by Tate and Brady was adopted by the Anglican Church, and endured as the standard work for the singing of psalms for more than a century. (source)

Lyrics to 
While shepherds watched their flocks by night

While shepherds watched
Their flocks by night
All seated on the ground
The angel of the Lord came down
And glory shone around
And glory shone around

"Fear not," he said,
For mighty dread
Had seized their troubled minds
"Glad tidings of great joy I bring
To you and all mankind,
To you and all mankind."

"To you in David's
Town this day
Is born of David's line
The Savior who is Christ the Lord
And this shall be the sign
And this shall be the sign."

"The heavenly Babe
You there shall find
To human view displayed
And meanly wrapped In swathing bands
And in a manger laid
And in a manger laid."

Thus spake the seraph,
And forthwith
Appeared a shining throng
Of angels praising God, who thus
Addressed their joyful song
Addressed their joyful song

"All glory be to
God on high
And to the earth be peace;
Goodwill henceforth
From heaven to men
Begin and never cease
Begin and never cease!"