The Sanhedrin was an assembly of Jewish religious and political leaders who served as an advisory board to the High Priest. It was composed of both Pharisees and Sadducees, two distinct sects of Judaism with different beliefs. The Pharisees believed in the authority of oral tradition and the resurrection of the dead, while the Sadducees believed only in the authority of the written Torah. In Matthew 16, Jesus warned his disciples to be wary of the Pharisees and Sadducees, saying that they were teaching false teachings and were ultimately untrustworthy.