'Hardness' in the Bible

On God my salvation and my glory rest;He is my rock of [unyielding] strength, my refuge is in God.

Your God has commanded your strength [your power in His service and your resistance to temptation];Show Yourself strong, O God, who acted on our behalf.

Who is like the wise man?And who knows the interpretation of a matter?A man’s wisdom illumines his face,And causes his stern face to beam.

You will harden their hearts;Your curse will be upon them.