hard of heart

References in classic literature ?
I say this only, that usury is a concessum propter duritiem cordis; for since there must be borrowing and lending, and men are so hard of heart, as they will not lend freely, usury must be permitted.
They loved the lamentable works of Ares and deeds of violence; they ate no bread, but were hard of heart like adamant, fearful men.
PRINCE GEORGE YOU would have had to be pretty hard of heart not to have shed a tear when baby Cambridge, right, was born THE LINDO WING THE wards at St Mary's Hospital were well regarded before but are now the most famous in the world.
ONLY the hard of heart could have watched unmoved last week as Gordon Ramsay's lambs were slaughtered.
Ezekiel will remind us that the pharaohs of the world are still hard of heart and rebellious against God's will.
Many in our society struggle with this issue but if we continue to be hard of heart towards homosexuals, it solves nothing and we are perceived as bigots.
My friend has been to speak to the person concerned and asked for forgiveness if she has committed a wrong, but the other person prefers to remain hard of heart.