The Gospels were written long ago and sometimes certain phrases come through that can be confusing to the modern ear. Such is the case with the "Chair of Moses" spoken about in the Gospel of Matthew.
Then Jesus spoke to the crowds and to his disciples, saying, “The scribes and the Pharisees have taken their seat on the chair of Moses. Therefore, do and observe all things whatsoever they tell you, but do not follow their example. For they preach but they do not practice.
What is the chair of Moses?
Various historians and scholars have investigated this passage and have come to the conclusion that Jesus was referring to the "office" of Moses and his legacy.
Frank McGloin gives the following explanation in his early 20th-century book, The Mystery of the Holy Trinity:
Sitting in the chair of Moses signified that the Scribes and Pharisees were in some way successors to the great law giver; that his office and authority had come down to them...[they believed] when sitting in the chair of Moses (that is, speaking in Sanhedrin assembled and officially; in other words, ex cathedra) had with them, for the purpose of guiding them in the correct rendition and application of the divine law, the same "Spirit of God" which had been imparted as Holy Writ declares, from Moses to his Council of Seventy Elders.
Chairs also had a practical significance, as often teachers in the ancient world would sit down when they taught. As a result, there was likely an actual chair that they sat on.
Jesus acknowledged that the scribes and Pharisees had a spiritual authority when interpreting the law and the prophets.
However, he did not want anyone to follow their example. As Jesus said, "they preach but they do not practice."