Here "heart" represents a person's mind. A person who does not think clearly and is unable to understand and care about what is happening is spoken of as if his heart were insensitive. AT: "Make these people unable to understand" or "Make the minds of these people dull" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-metaphor]])
This command means that Yahweh will use Isaiah's message to cause the people to understand even less and to make them less sensitive to what Yahweh is doing.
"make it so that they cannot hear, and make it so that they cannot see." Isaiah making people to not understand Yahweh's message or what he is doing is spoken of as if Isaiah were making them deaf and blind. (See: [[rc://en/ta/man/translate/figs-metaphor]])
# they might see with their eyes, hear with their ears
People being able to understand Yahweh's message and what he is doing is spoken of as if the people were able physically to see and hear. (See: [[rc://en/ta/man/translate/figs-metaphor]])
# understand with their heart
Here "heart" represents as person's mind. Truly understanding something and caring about what is happening is spoken of as if the people were to understand with their hearts. (See: [[rc://en/ta/man/translate/figs-metonymy]])
# then turn
Repenting and starting to obey Yahweh is spoken of as if the people were physically to turn towards him. AT: "follow me again" or "then start trusting in me again" (See: [[rc://en/ta/man/translate/figs-metaphor]])