The Jebusite hypothesis is the idea that the high priest Zadok was a native Jebusite priest. It was first proposed by Aage Bensen in 1933 to account for the many discrepancies in Zadok’s genealogies in the Deuteronomistic History and Chronicles and gained widespread support in the mid-20th century. According to this theory, David installed Zadok as high priest after conquering Jerusalem in order to win the support of his new Jebusite subjects. Zadok’s appointment also facilitated the identification of Yahweh with the Jebusite deity El Elyon mentioned in Genesis 14:18. At the same time, his foreign origin necessitated the convoluted genealogies in the Deuteronomistic History and Chronicles. Proponents of the Jebusite hypothesis note that Zadok comes from the root ṢDQ, which also occurs in the names’ of several pre-Israelite inhabitants of Jerusalem (e.g. Melchizedek in Genesis 14:18 and Adoni-zedek in Joshua 10:1).
Frank Moore Cross was critical of the Jebusite hypothesis, noting that the root ṢDQ is a common element in Northwest Semitic names and that David is depicted as a devout Yahwist in the Deuteronomistic History who would never appoint a foreign priest. Insetead, he suggested that Zadok was an Aaronid priest.
Ramsey, George W. “Zadok.” In The Anchor Bible Dictionary VI., edited by David Noel Freedman, 1034-1036. New York: Doubleday, 1992.