This tune, WEXFORD CAROL, is an old Irish favorite, possibly going back as far as the 12th century. It is often used with the Christmas lyrics that begin "Good people all, this Christmastime." The tune is also sometimes known as ENNISCORTHY CAROL (from the town in County Wexford where it was found and transcribed from a local singer by William Grattan Flood (1859 - 1928), who was organist and musical director at St. Aidan’s Cathedral in Enniscorthy). It became more widely known after inclusion in "The Oxford Book of Carols."

"God Promised a Son" is a new text, suitable for Advent or when any of the related scriptures are being used. It has been especially useful for "Lessons and Carols" services. It tells the story of two of the many miraculous births that point to the ultimate miraculous birth - that of Jesus Christ.

The transpose button is enabled in case you’d like this in another key, e.g. lower a half step to the key of D for easier guitar chords or a step higher so the first note isn't so low.

I have also posted a simple piano/vocal arrangement of this carol, as well as a choral anthem here on Score Exchange. See above related scores for those and other Advent scores.