The Pharisees were very adamant in rejecting Jesus! They asked Jesus who He is.
Jesus replied that He said who He says He was "from the beginning" (8:25). From a look back at the entire conversation in John 8, Jesus proclaimed that he is sent by the Father and is not of the world. And from conversations in John 5, Jesus talked about how he provides a way to get everlasting life. It's heavily implied that the Pharisees' question on Jesus is not to learn about Jesus but to accuse Jesus.
Jesus also talked about he has things he can say and judge regarding the Pharisees (just not at that time). He got such things from the Father, and Jesus heard from the Father (8:26). Jesus's teachings have support for the Father, so when the Pharisees rejected Jesus's teachings, they technically also rejected the Father's teachings. In fact, even though Jesus stated that he was sent by the Father back in 8:18, regarding the one who sent Jesus, the Pharisees "did not understand" (8:27). Based on the Pharisees' attitudes, the lack of understanding is based on the refusal to understand Jesus.