John 12:36-43 (ESVST)
While you have the light, believe in the light, that you may become sons of light.
When Jesus had said these things, he departed and hid himself from them. 37 Though he had done so many signs before them, they still did not believe in him, 38 so that the word spoken by the prophet Isaiah might be fulfilled:
“ Lord, who has believed what he heard from us,
and to whom has the arm of the Lord been revealed?”
39 Therefore they could not believe. For again Isaiah said,
40 “He has blinded their eyes
and hardened their heart,
lest they see with their eyes,
and understand with their heart, and turn,
and I would heal them.”
41 Isaiah said these things because he saw his glory and spoke of him.
John here answered the question that I beleive most of us wanted to ask or were already asking. Why did the Jews fail to beleive in Jesus despite all the signs he had done among them? John is saying the answer to this question is that, the Jews’s unbelief was foretold by the scripture through Isaiah the prophet. John quotes Isaiah 53:1 and 6:10. So, this widespread unbelief was the fulfillment of not only scripture but of prophecy.
42 Nevertheless, many even of the authorities believed in him, but for fear of the Pharisees they did not confess it, so that they would not be put out of the synagogue; 43 for they loved the glory that comes from man more than the glory that comes from God.
Excommunication, that is, being kicked out of the synagogue, was reported as early as the time of Ezra (10:8), but there is practically no information about the way it was practiced in New Testament times. The synagogue was the center of Jewish community life, so excommunication cut a person off from many social relationships (though, in some forms, at least in later times, not from worship). This is what the authorities were afraid of and although they believed in Jesus, they did not confess it. Instead of seeking the recognition and the praise from God, they chose the recognition and the praise of their fellow Jews.