Camille Saint-Saën's Christmas Oratorio

Yester-day, I listened to almost all of the music I have by Camille Saint-Saëns, including his Christmas Oratorio.  I’ve listened to this only a few times, no more than five, but listening to it yester-day, I found something interesting.

In the second movement - Recit et chœur - I recognized the melody from the chant “The Glory of the Father.”  Roughly, measures 3 to 8 in this part (found here):

Originally, I had assumed that Saint-Saëns was quoting an older chant [It’s not uncharacteristic for Saint-Saëns to quote other melodies in his works.  He includes “Dies Irae” in “Danse Macabre” (I found it once, but I confess I can’t seem to find it again), and he later quotes from his own “Danse Macabre” in the “Fossils” section of Carnival of the Animals.], but I looked up some things and now I think it’s the opposite way around - that the chant is quoting Saint-Saëns.

"The Glory of the Father" was written by Egil Hovland, who was born in 1924.  Saint-Saëns’ Christmas Oratorio was written in 1858.  It would truly be a feat to quote from a chant that would not be written for at least sixty years.

But the melodies are so similar that I find it hard to believe that this is just a coincidence.  The corresponding texts to each of these melodies are “Et in terra pax” (and on earth peace) in Saint-Saëns’ oratorio and “In Him was life” in Hovland’s chant.  I don’t know if Hovland intended connections to be drawn between these two texts by using a very similar, if not the same, melody.  But then again, I don’t even know if he intentionally used Saint-Saëns’ melody.