'Hard' in the Bible

Now Saul, still breathing threats and murder against the disciples of the Lord [and relentless in his search for believers], went to the high priest,

“For the heart (the understanding, the soul) of this people has become dull (calloused),And with their ears they scarcely hear,And they have shut their eyes [to the truth];Otherwise they might see with their eyes,And hear with their ears,And understand with their heart and return [to Me],And I would heal them.”’