John 12:37

But though he had done so many miracles before them
Openly, and in the presence of them; meaning those miracles which were done at Jerusalem, as those which brought Nicodemus to him, and to an acknowledgment of him as a teacher sent from God; and particularly the cure of the lame man at Bethesda's pool, the giving sight to the man that was born blind, by anointing his eyes with clay, and sending him to wash in the Pool of Siloam, and the raising Lazarus from the dead at Bethany, which was within two miles of Jerusalem, in the presence of many of them who were come there to comfort Martha and Mary. Yet

they believed not on him;
the miracles done by Christ before their eyes, which they could not deny, nor disprove, and were so many, and so great, were aggravations of their unbelief; and such indeed is the nature of that sin, and so deeply rooted is it, that the most powerful means, and mighty works, will not bring a person to believe in Christ, without the powerful and efficacious grace of God.