‘I will give you a new heart and put a new spirit within you: I will take the heart of stone out of your flesh and give you a heart of flesh.‘
(Ezekiel 36:26, NKJV)
This is a new birth. The heart of flesh is a warm, kind, loving heart. It is the heart – or spirit – of Jesus, (even when the person doesn’t know this).
Were someone with the spirit of Jesus to hear that a group of people were injuring children with bombs, and that some of the injured needed an arm or leg amputated, and that the amputations were being done without anaesthetic because the bombers had cut off medical supplies, they would be distraught. They might well lie awake at night thinking about these poor children.
In contrast, someone with a heart of stone might even try to justify this cruelty – perhaps on political or religious grounds.