I think it would make for sense for you if read it as "Benedicite, Deus", reading that as the vocative, "O God".
It's extremely difficult to translate this in modern English. I can't think of a good one off the top of my head.
For example, at the very lengthy Roman grace before meals, one begins by singing the versicle:
I think the Anglicans translated this as "Bless ye", which is silly sounding, as is "Give the blessing"/"Give the blessing" (I'd be waiting for someone to say, "will someone just bless the food so we can eat?")
Thanks again, Timothy--I'm finding this very helpful. I hope you won't be irritated if I ask just one more question, because I'm still a little confused.
I suppose treating "Deus" as a vocative helps a little, but it still doesn't explain, at least as far as I can see, the 2nd person plural of "benedicite". Usually the vocative case is for direct address (as you translate it above). But when the verb is in the 2nd plural imperative, the address is to a group of persons. Are you suggesting that this will be OK, grammatically, since "Deus" refers to a Trinity of Persons, or do you see the grammar working some other way?
I don't mean to be so dense, I'm just trying to make sense of the grammar--I do thank you for your patience!