This was to fulfill the word of Isaiah the prophet:
“Lord, who has believed our message
and to whom has the arm of the Lord been revealed?”
For this reason they could not believe, because, as Isaiah says elsewhere:
“He has blinded their eyes
and hardened their hearts,
so they can neither see with their eyes,
nor understand with their hearts,
nor turn—and I would heal them.”
Isaiah said this because he saw Jesus’ glory and spoke about him.
Yet at the same time many even among the leaders believed in him. But because of the Pharisees they would not openly acknowledge their faith for fear they would be put out of the synagogue; for they loved human praise more than praise from God.
Source: Daily Manna