'Hard' in the Bible

For thou art not sent to a people of a strange speech and of a hard language, but to the house of Israel;

not to many peoples of a strange speech and of a hard language, whose words thou canst not understand. Surely, if I sent thee to them, they would hearken unto thee.

But the house of Israel will not hearken unto thee; for they will not hearken unto me: for all the house of Israel are of hard forehead and of a stiff heart.

Behold, I have made thy face hard against their faces, and thy forehead hard against their foreheads.