Commenting on Heb 7:12, biblical scholar Craig R. Koester noted the following:
7:12. For when there is a change of the priesthood. This runs counter
to the idea that the Levitical priesthood was permanent (Exod 40:15; Num 18:19;
25:13). The high priesthood was changed from one house to another within
the Levitical family (Josephus, Ant.
12.387), but when the Syrians changed the practice (1 Macc 7:5–9; 10:20; 11:27;
2 Macc 4:24, 29; 14:3), many Jews protested (T. Mos. 6:6; 7:9–10; 1QpHab VIII, 8–9; XI, 4–8; 4QpPs 37 II,
17–19). Hebrews, however, speaks not about a change within the Levitical
family, but a change from the Levitical priesthood to a different type of
priesthood. (Craig R. Koester, Hebrews:
A New Translation with Introduction and Commentary, [AYB 36; New Haven:
Yale University Press, 2008], 354, emphasis in bold added)
Of course, I believe this is a misinterpretation of the
meaning of μετατίθημι in Heb 7:12. Further, it shows that only Latter-day
Saint theology helps preserve the consistency between the New and Old Testaments
on this issue.