In the worship of Assur, accordingly, a tendency to monotheism reveals itself. The tendency was even more pronounced in a certain literary school of thought in Babylonia. We have texts which resolve the deities of the popular faith into forms of one god; sometimes this is Anu of Erech, sometimes it is Merodach of Babylon.
Babylonian worship necessitated a large hierarchy of priests. At the head was the high-priest, who in early times possessed temporal power and in many states was the predecessor of the king. The king, in fact, inherited his priesthood from him, and was consequently qualified to perform priestly functions. Under the high-priest there were numerous classes of ministers of the gods, such as the “anointers,” whose duty it was to anoint the holy images with oil, the ordinary “priests,” the “seers,” and the “prophets.” The prophets enjoyed high consideration; they even accompanied the army to the field, and decided whether the campaign would result in victory or defeat. Quite apart from all these were the astrologers, who did not belong to the priesthood at all. On the contrary, they professed to be men of science, and the predictions of the future which they read in the stars were founded on the records and observations of former generations.
A chief part of the duty of the priests consisted in offering sacrifice and reciting the services. The sacrifices were of two kinds, as in the Jewish ritual. The same animals and the same fruits of the earth were offered by both Babylonians and Israelites, and in many cases the regulations relating to the sacrifices were similar. The services were elaborate, and the rubrics attached to the hymns and prayers which had to be recited are minute and complicated. The hymns had been formed into a sort of Bible, which had in time acquired a divine authority. So sacred were its words, that a single mispronunciation of them was sufficient to impair the efficacy of the service. Rules for their pronunciation were accordingly laid down, which were the more necessary as the hymns were in Sumerian. The dead language of Sumer had become sacred, like Latin in the Middle Ages, and each line of a hymn was provided with a translation in Semitic Babylonian.
In appearance, a Babylonian temple was not very unlike those of Canaan or of Solomon. The image of the god stood in the innermost shrine, the Holy of Holies, where also was the mercy-seat, whereon it was believed, as upon a throne, the deity was accustomed to descend at certain times of the year. In the little temple of Balawat, near Nineveh, discovered by Mr. Hormuzd Rassam, the mercy-seat was shaped like an ark, and contained two written tables of stone; no statue of the god, however, seems in this instance to have stood beside it. In front of it was the altar, approached by steps.