Government by religious authority is a structural form rather than a legal innovation with one founding document, and it has arisen independently, more than once, in civilisations separated by continents and millennia. Even the word theocracy postdates the practice by centuries, coined by Josephus in the first century to describe an already-old government rather than a newly founded one, so the word's own origin cannot supply a year either.
What would resolve this A scholarly consensus naming one reference case for theocracy's origin, the way a single set of reforms settles the question for direct democracy, rather than the several independently credited exemplars, the Sinai covenant and the era of Moses in ancient Israel, the 754 Donation of Pepin founding the Papal States, and Iran's 1979 Islamic Republic, presently named across general reference works with no one privileged over the others.
OpenComparative political science, history of religion and governmentAtlas Relation Vocabulary