Very pretty, and you struck a nice mixing balance between vocals and instruments. I am not religious, but I still appreciated the beauty of the work and your expression of your own faith.
My one constructive suggestion might be to tinker a bit with the reverb. A song like this cries out to be heard in the acoustics of a monastery, but the reverb here seems a little generic. If your DAW is able, perhaps a more complex reverb setup that mimics a stone building would give it that extra little authentic touch. Still, it's very nice work!
Your wife's vocal quality is lovely; she reminds me a little of Maddy Prior from Steeleye Span, in that group's rendition of Gaudete (on the album Below the Salt).