Israel (that’s the Northern Kingdom of Israel) suffered a series of ‘bad’ kings: all but two were assassinated and one lasted only a month. During this time, God sent a series of prophets (including Hosea) to warn them, but to no avail.
Israel had now dismissed any idea of taking God seriously, just as Pharoah had some centuries earlier. And just as Pharoah suffered the consequences, and God watched his heart be hardened, Israel also was about to suffer the same.
Isaiah delivered this message to Israel:
Isaiah 6:9-10 Listen carefully, but do not understand.
Watch closely, but learn nothing.
Harden the hearts of these people.
Plug their ears and shut their eyes.
That way, they will not see with their eyes,
nor hear with their ears,
nor understand with their hearts
and turn to me for healing.
This message, that Israel was not seeing with their eyes, and not hearing with their ears’ is similar to Jeremiah’s words to Judah during its last days:
Jeremiah 5:21-22 Listen, you foolish and senseless people,
with eyes that do not see
and ears that do not hear.
Have you no respect for me?
Why don’t you tremble in my presence?
The disciples would have had to have known this is what Jesus was referring to when he threw them the same challenge when they argued over a lack of bread in the boat, just after Jesus had fed 4000 people:
Mark 5:17 Jesus knew what they were saying, so he said, ‘Why are you arguing about having no bread? Don’t you know or understand even yet? Are your hearts too hard to take it in?’