Matthew 2:4

And when he had gathered all the chief priests and scribes of the people together--The class of the "chief priests" included the high priest for the time being, together with all who had previously filled this office; for though the then head of the Aaronic family was the only rightful high priest, the Romans removed them at pleasure, to make way for creatures of their own. In this class probably were included also the heads of the four and twenty courses of the priests. The "scribes" were at first merely transcribers of the law and synagogue readers; afterwards interpreters of the law, both civil and religious, and so both lawyers and divines. The first of these classes, a proportion of the second, and "the elders"--that is, as LIGHTFOOT thinks, "those elders of the laity that were not of the Levitical tribe"--constituted the supreme council of the nation, called the Sanhedrim, the members of which, at their full complement, numbered seventy-two. That this was the council which Herod now convened is most probable, from the solemnity of the occasion; for though the elders are not mentioned, we find a similar omission where all three were certainly meant (compare Mat 26:59; Mat 27:1). As MEYER says, it was all the theologians of the nation whom Herod convened, because it was a theological response that he wanted. he demanded of them--as the authorized interpreters of Scripture. where Christ--the Messiah. should be born--according to prophecy.

— Jamieson-Fausset-Brown Commentary (public domain)