Matthew 23:2
Just before launching into a blistering denunciation of the scribes and Pharisees, Jesus delivers this command to the crowds: "The scribes and Pharisees sit on Moses’ seat; so practice and observe whatever they tell you, but not what they do; for they preach, but do not practice" (Matt. 23:2-3).
Although Jesus strongly indicts his opponents of hypocrisy for not following their own teaching, he nevertheless insists that the scribes and Pharisees hold a position of legitimate authority, which he characterizes as sitting "on Moses’ seat." One searches in vain for any reference to this seat of Moses in the Old Testament. But it was commonly understood in ancient Israel that there was an authoritative teaching office, passed on by Moses to successors.
As the first verse of the Mishna tractate Abôte indicates, the Jews understood that God’s revelation, received by Moses, had been handed down from him in uninterrupted succession, through Joshua, the elders, the prophets, and the great Sanhedrin (Acts 15:21). The scribes and Pharisees participated in this authoritative line and as such their teaching deserved to be respected.
Jesus here draws on oral Tradition to uphold the legitimacy of this teaching office in Israel. The Catholic Church, in upholding the legitimacy of both Scripture and Tradition, follows the example of Jesus himself.
In addition, we see that the structure of the Catholic Church—with an authoritative teaching office comprised of bishops who are the direct successors of the apostles—follows the example of ancient Israel. While there are groups of Christians today that deny continuity between Israel and the Church, historic orthodox Christianity has always understood the Church to be a fulfillment of Israel. This verse about Moses' chair illuminates why we say that the successor of Peter, when he gives a solemn teaching for the whole Church, is said to speak <ex cathedra> or "from the chair."
Whereas under the Old Covenant the administration of God’s people came from the "chair of Moses," Christians under the New Covenant look to the "chair of Peter" for direction on questions of faith and morals. But there is a notable difference between the magisterium under the Old Covenant and our teachers under the New Covenant. The successors of the apostles, and especially Peter’s successor, have the Holy Spirit to guide them into all truth, and they have Jesus’ promise that the "gates of hell will not prevail" against the Church (Matt. 16:17-19). ref
He also condemned their tradition on more than one occasion.......
Very good explanation; Protestantism, including its derivatives Evangelicalism and Restorationist movements do not have this authority; they are separated from the Apostles by a wide historical gulf despite trying to re-form Christianity after their own image, so to speak.