Looking at the Pharisees and the “Chair of Moses”, and comparing it to the Apostles and the “Chair of Peter”, it is not a comparison of infallibility per se, so much as it is a comparison of respect for human authority. Jesus sets the tone for believers as He fully recognizes and supports the teaching authority of the sinful Pharisees, and this relates directly to the eventual Apostolic teaching authority the 12 would gain from Christ Himself. They themselves would not be free from sinful behavior, but their seat of authority must be respected. The charism of infallibility (protection from teaching error) is what would set the Apostles (and their successors) apart from the Pharisees (who themselves were successors of the Sanhedrin). So again, it was not a comparison for the sake of infallibility, so much as it was a comparison to human authority.
Here’s an extract from a
Catholic.com article: Oral Tradition in the NT:
*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.” [David Hill informs us that Moses’ seat was “not simply a metaphor. There was an actual stone seat in front of the synagogue where the authoritative teacher (usually a scribe) sat.” The Gospel of Matthew (Grand Rapids: Eerdmans, 1990), 310.] 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 Abote 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. L. Sabourin, The Gospel According to St. Matthew (Bombay: St. Paul Publications, 1982), vol. 2, 793.]
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.
*
God Bless