Most religions use for their liturgy, scripture, and all “weighty” writings an archaic language that is no longer used (or was never used) as a means of everyday communication. The Roman Catholics have Latin, the Eastern Orthodox have Slavonic, the muslims have classical Arabic, the Hindus have Sanskrit, the Buddhists have Pali and classical Tibetan, etc. etc.
Why? Because such a language affords a certain mental (and therefore practical) insulation and buffering from the prosaic thought that vernacular language is associated with. You see, a language corresponds to a certain way of thinking, as anyone who speaks multiple very different languages can confirm. (English and Spanish isn’t a strong example, because they’re still too similar. English and Japanese would be a good example.) When you switch to a (very) different language, you become a slightly different person, because the other language simply works differently, requires and enables different things, different kinds of thoughts, and is even associated with different memories.
Having a language dedicated entirely to religious writing (and reading) allows one to switch to one’s “religious mind” by switching to that language. (Of course there are other ways of switching to one’s religious mind; but a different language is definitely a helpful instrument.)