This is another of the songs CWB sourced from the Resource Collection of Hymns and Service Music for the Liturgy from ICEL, which can still be purchased at GIA.
The text for Advent and Christmas is by Omar Westendorf based on Isaiah 40:1-11, and is set to Robert Edward Kreutz‘s FIDDLERS GREEN. Since Westendorf founded WLP, I suppose he is owned by GIA now.
I couldn’t find the text anywhere but it does show up in Worship 3rd ed. if you have that, or you could listen to the clip below.