6And the sons of Moses, according to the Holy Priesthood which he received under the hand of his father-in-law, Jethro; 7And Jethro received it under the hand of Caleb; 8And Caleb received it under the hand of Elihu; 9And Elihu under the hand of Jeremy; 10And Jeremy under the hand of Gad; 11 And Gad under the hand of Esaias; 12And Esaias received it under the hand of God. 13Esaias also lived in the days of Abraham, and was blessed of him— 14Which Abraham received the priesthood from Melchizedek, who received it through the lineage of his fathers, even till Noah; 15And from Noah till Enoch, through the lineage of their fathers; 16And from Enoch to Abel, who was slain by the conspiracy of his brother, who received the priesthood by the commandments of God, by the hand of his father Adam, who was the first man— 17Which priesthood continueth in the church of God in all generations, and is without beginning of days or end of years. 18And the Lord confirmed a priesthood also upon Aaron and his seed, throughout all their generations, which priesthood also continueth and abideth forever with the priesthood which is after the holiest order of God. (D&C 84:6-18)
As the last verse indicates, the priesthood being spoken of in verses 6-17 is the Melchizedek priesthood. We learn in Section 84 (verses 23-27) that the Melchizedek priesthood was taken from the children of Israel. But it apparently continued on the earth in an alternate line. In fact, Moses did not receive it through the lineal passing of priesthood from father to son (since obviously he didn't grow up with his natural father). Interestingly, he didn't receive it from anyone of the birthright lineage. Moses, though presumably a descendant of Abraham, did not receive the Melchizedek priesthood from a descendant of Abraham. He received it from his father-in-law -- Jethro, the high priest of Midian, who also is known in the Bible as Hobab or Reuel or Raguel, meaning “friend of God.”
When Moses continued on his journey, he invited Jethro to come with him, but Jethro turned down his invitation and remained with his own people (Numbers 10:29-30). As far as I can tell from the passage in the Doctrine & Covenants about Moses’ line of authority, it is completely independent of Abraham. Esaias received it directly from God, as (presumably) Abraham did. [Thanks to Nathan for the correction.]
So what happened to the Melchizedek priesthood that Jacob and Joseph held? Was it not passed from father to son among the Israelites? What of the birthright of Joseph? Was it not something having to do with the Melchizedek priesthood? What are we to make of a completely separate group’s line of authority? Did Jethro's descendants continue the Melchizedek priesthood after it had been taken away from the children of Israel? Could there also have been another line of Melchizedek priesthood authority in, say, China, at the same time? Does this have any implications for us today? (If not, why include it in the Doctrine & Covenants?)
And if there were alternate lines of Melchizedek priesthood authority, why do we emphasize Abraham, Isaac, and Jacob so much? Did God make covenants with them, but not with others to whom he directly gave the priesthood? Doesn't the Melchizedek priesthood hold all the keys of the Abrahamic covenant? Do we emphasize Abraham primarily because we happen to have records passed down to us in the Bible that figure him as a prominent figure? If we had received the records of the Midianites instead of the Israelites, would we speak of the Esaian covenant or the Raguelic covenant instead of the Abrahamic covenant? Does this influence our understanding of Israel as a chosen people or lineage?
