Different Priesthoods for Different Covenants

Torah portion Vayeshev (Genesis 37-40), contains one of many stories of misdeeds and poor decisions of the patriarchs. In this particular episode, Tamar, the widow of Judah's son, disguises herself as a prostitute in order to trick Judah into sleeping with her. He has no idea it was her, and three months later, when he learns that she is pregnant, he suggests that she be burned as punishment.

That seems excessive, but there's always more to the story than the bare text might imply.

Leviticus 21:9 prescribes burning as punishment for the daughter of a priest "if she profanes herself by whoring, profanes her father". Since Tamar was accused of "whoring", some believe that she was the daughter of a priest. Clearly she was not the daughter of a Levitical priest, because the Levitical priesthood would not be instituted until a few generations later. If her father was a priest, then he was a priest of some other order, one we don't know anything about.

Every covenant between a god and mankind requires the mediation of a priesthood. In many cases, that priesthood is as simple as the father or eldest son. In some cases, the priesthood might be large and complex with castes and compartmentalized responsibilities, like that of Aaron and his sons. The requirements, rituals, and laws that govern each priesthood are necessarily different because they have different purposes, serve different covenants, and often even different gods. 

Keep that in mind as you read this article I recently wrote for Founded in Truth: Priests, Laws, and Covenants in Hebrews 7-8.