
It's not by mistake. Although it was also released as a standalone single, "The Prayer" is also featured in the soundtrack of Quest For Camelot (1998).

Sorry, my interface isn't set in English at the moment so perhaps I misunderstood. 😳

The song was written originally for the movie, and alternative versions of such songs (e.g. end credits versions) can be added to the performer's page (instead of the movie one), but the soundtrack it comes from is still to be listed among the featured artists.
This is to distinguish such songs from already existing songs which are just used in a movie. In such instances, the soundtrack can be listed as an "also performed by" artist.
@BlackRyder letting you know why your edit was reverted.

Got it, thanks for the explanation and the edit, Icey!

Hi Igor, thanks for the heads-up. I've erased the 'Quest for Camelot' info because this is pretty much a reworked version of the song that ended up having no connection with said soundtrack. In any case, Dion herself released a new solo version of the song--renamed 'A Mother's Prayer', and with an arrangement that echoes the one with Bocelli--in her album 'Miracle' (2004). That one is added on her lyrics page as well, and I've added a link to the original soundtrack version on that page. I think it makes things way clearer :)
@BlackRyder , @Icey
One of you two inserted Quest for Camelot (OST) into Featuring Artist field apparently by mistake meaning Also Performed By field.
If I don't hear from you for a couple of days I'll make the correction myself.