A seat or chair — used for the seat of Moses (the authoritative teaching chair) and for the money-changers' seats in the Temple.
The Greek kathedra (origin of the English 'cathedral') means a chair or seat, especially one of authority. It appears three times in the NT: Matthew 21:12 and Mark 11:15, where Jesus 'overturned the tables of the money changers and the kathedras of those selling doves'; and Matthew 23:2, where Jesus says 'The teachers of the law and the Pharisees sit in Moses' seat (kathedra).' A 'cathedral' is literally the church with the bishop's chair — the teaching seat.
The kathedra of Moses in Matthew 23:2 is a physical seat in the synagogue from which the Torah was authoritatively read and interpreted. Jesus acknowledges its authority while condemning the hypocrisy of those who occupy it: 'do what they say, not what they do.' Then in Matthew 21, Jesus overturns the kathedras of the dove-sellers — the very seats of commercial religion within the Temple courts. The seat of teaching authority is holy when it serves God's people; it becomes a den of thieves when it exploits them. The cleansing of the Temple is Jesus asserting a higher teaching authority than any kathedra.