'Hard' in the Bible

The king's request is a very hard one, and there is no other who is able to make it clear to the king, but the gods, whose living-place is not with flesh.

Because a most special spirit, and knowledge and reason and the power of reading dreams and unfolding dark sayings and answering hard questions, were seen to be in him, even in Daniel (named Belteshazzar by the king): now let Daniel be sent for, and he will make clear the sense of the writing.

And I have had news of you, that you have the power of making things clear, and of answering hard questions: now if you are able to make out the writing and give me the sense of it, you will be clothed in purple and have a gold chain round your neck and be a ruler of high authority in the kingdom.

But when his heart was lifted up and his spirit became hard with pride, he was put down from his place as king, and they took his glory from him:

In the third year of Cyrus, king of Persia, a secret was unfolded to Daniel, whose name was Belteshazzar; and the thing was true, even a hard work: and he had knowledge of it, and the vision was clear to him.