What does John 7:19 mean?

Here, Jesus once again attacks the self-righteous, self-confident, self-centered religion of Jerusalem's spiritual leaders. To the people of Israel, there was no more important figure than Moses, and no ideal higher than following the laws given to Israel by Moses. For Jesus to criticize their adherence to the law was an attack on their very sense of identity. This is a criticism Jesus has posed in the past (John 5:39–47), and will bring up again (John 8:39–44). This meshes with the point Jesus made in verses 17 and 18, that those who refuse to obey God will not understand the truth. Worse, their refusal to accept Jesus is, in effect, a rejection of the very Scriptures they claim to uphold.

Despite the crowd's skepticism (John 7:20), Jesus is well aware that the religious leaders of Jerusalem have sought to kill Him as a blasphemer (John 5:18). He is well aware that their rejection of Him is not superficial—it is deadly serious (John 7:1). And, it proves the very prediction made by Jesus in the early verses of this chapter: convicting the world of sin earns the world's hatred (John 7:7).