I was intrigued to see the name “Isaac Watts” as the author of the lyrics. He's known as the author of many famous hymns, including “When I Survey the Wondrous Cross” and “Oh God, Our Help in Ages Past.” So it wouldn't be surprising for him to have written about Christmas. A little digging, though, shows that his lyrics are drawn from a collection he wrote titled Psalms of David Imitated in the Language of the New Testament. His goal was to take a selection of Hebrew Psalms, in particular the ones attributed to David, and re-write them to fit into a singable meter and, more importantly to him, into Christian doctrine. Our supposed carol is actually the last half of Psalm 98. Here are the words of the verses usually included, taken from the King James Bible:
Make a joyful noise unto the Lord, all the earth: make a loud noise, and rejoice, and sing praise. Sing unto the Lord with the harp; with the harp, and the voice of a psalm. With trumpets and sound of cornet make a joyful noise before the Lord, the King. Let the sea roar, and the fulness thereof; the world, and they that dwell therein. Let the floods clap their hands: let the hills be joyful together before the Lord; for he cometh to judge the earth: with righteousness shall he judge the world, and the people with equity.
Watts has re-written the above to refer specifically not to the first coming of Christ to earth but to the second, not to the humble birth in the stable but to the coming in triumph when “the Savior reigns.” When you realize the source of the song the words begin to make more sense. So the line, “While fields and floods, rocks, hills and plans/Repeat the sounding joy” might imply that the song of the angels to the shepherds was echoing all around the landscape. That's what I've always vaguely thought, anyway. The psalm clearly refers, though, to God's coming in judgment to set all things right, an event so joyous that even the “floods clap their hands.” (Isn't that a great image?) God's blessings will then flow “far as the curse is found.” Watts is referring to the curse of sin put on humankind when Adam and Eve disobeyed God in the Garden of Eden, but we don't typically stop and think, “What curse?” The last verse clearly portrays a world under the direct rule of God: He makes the nations prove (show the truth of) His glorious righteousness.
So how did this hymn become known as a Christmas carol? It's not completely clear, but what we do know is that Lowell Mason, a leading American church musician, published it in 1839, adapting the words to an old hymn tune. I can't tell if Mason categorized it as a Christmas carol or if that came later. It's now firmly established as a part of this season, though, and who would want to do away with that connection? Understanding the original intent of its author can only enrich our enjoyment as we sing its beautiful words.