Even in Old Testament times religious teachers, were assigned religious duties were separate.
The Old Testament (The Levites) had a completely separate group of people, who were assigned holy duties. The separation even included they did not having an inheritance, God was there inheritance.
20 And the LORD spake unto Aaron, Thou shalt have no inheritance in their land, neither shalt thou have any part among them: I am thy part and thine inheritance among the children of Israel.
21 And, behold, I have given the children of Levi all the tenth in Israel for an inheritance, for their service which they serve, even the service of the tabernacle of the congregation.
22 Neither must the children of Israel henceforth come nigh the tabernacle of the congregation, lest they bear sin, and die.
Most of the rules laid out in the Old Testament (an exception is the 10 commandment) were applied to a very specific region. His promised land, and not America.
Leviticus 18 (King James Version)
24 Defile not ye yourselves in any of these things: for in all these the nations are defiled which I cast out before you:
25 And the land is defiled: therefore I do visit the iniquity thereof upon it, and the land itself vomiteth out her inhabitants.
26 Ye shall therefore keep my statutes and my judgments, and shall not commit any of these abominations; neither any of your own nation, nor any stranger that sojourneth among you:
27(For all these abominations have the men of the land done, which were before you, and the land is defiled;)
28 That the land spue not you out also, when ye defile it, as it spued out the nations that were before you.