Matthew 23:2

ἐπὶ τ. Μ. καθέδρας, on the seat of Moses, short for, on the seat of a teacher whose function it was to interpret the Mosaic Law. The Jews spoke of the teacher's seat as we speak of a professor's chair. ἐκάθισαν, in effect, a gnomic aorist = solent sedere (Fritzsche), not a case of the aorist used as a perfect = have taken and now occupy, etc. (Erasmus). Burton (Syntax) sees in this and other aorists in N. T. a tendency towards use of aorist for perfect not yet realised: “rhetorical figure on the way to become grammatical idiom, but not yet become such,” § 55. οἱ φαρ. Wendt (L. J., i., 186) thinks this an addition by the evangelist, the statement strictly applying only to the scribes.