Hmm I have been thinking about this topic quite a bit recently. If you want to say a prayer it is nothin but an invocation to an entity. So, in the end it does not really matter if you want to summon a demon or pray to an archangel because it is the same. There is no good or evil. The thing is, back in time there might me something similar to magic, real spellcasting.
Specially if we look of how people in the past treated the dead. For example Mos Teutonicus:
''The process of
mos Teutonicus began with the
cadaver being
dismembered[3] to facilitate the next stage in the process, in which the body parts were
boiled in water or wine
[3] for several hours.
[2] The boiling had the effect of separating the flesh from the
bone. Any residual was scraped from the bones, leaving a completely clean
skeleton.
[2] Both the flesh and
internal organs could be buried immediately, or
preserved with
salt in the same manner as animal meat.
[3] The bones, and any preserved flesh, would then be transported back to the deceased's home for ceremonial interment.''
They believed in the end of the days that the dead will once again rise up and fight.
But what I wanted to try out is to drink some holy water though. Whatever it takes...