This is John's testimony, when the Jews sent priests and Levites from Jerusalem to ask him, "Who are you?"
Priests and Levites ... Most of the high priestly class were Sadducees, and it is remarkable that some of the delegation were Pharisees (John 1:24).  The mutual hatred of those sects raises a question of how the Pharisees came to have a part in the inquiry; but one obvious explanation is found in the invariable tendency of bitterest enemies to unite in a common opposition to Christ.  These same two sects made common cause against Jesus  (Matthew 22:23-40), despite the fact that Jesus had publicly triumphed over the Sadducees in their position on the resurrection, and despite the further fact that the Pharisees themselves also rejected the Sadducees' position.  Those who attribute any mistake to John in his identifying Pharisees as party to the investigation must do so upon an unjustifiable presumption.