Tears came to the eyes of Umar ibn Abdulaziz, and he replied, ‘It is as you have said.’ Then he ordered that their needs be satisfied from the Treasury. The Nomad (spokesman) requested permission to leave, and Umar ibn Abdulaziz said to him, ‘O’ man, you have stated the case of God’s slaves to me. State my case likewise to Allah the exalted!’ The Bedouin turned his face to the sky and said, ‘O’ Lord. In your strength and glory do for Umar Ibn Abdulaziz what he has done for your slaves.’
At that very moment a cloud came up and rain began to fall. During the rainstorm a large hailstone came down, and dropped onto a baked brick and broke. Out of it came a letter, which said, ‘This is a warrant from me, Allah the exalted, to Umar ibn Abdulaziz. I have exempted Umar ibn Abdulaziz from the hellfire.’
Imam Ghazali Counsel for Kings p.68 translated by F.R.C. Bagley
See post on Supplication/Dua'
Umar ibn Abdulaziz (may bestow upon him mercy) was the khalifh of the Muslim world from 717-720. He is sometimes referred to as the fifth rightly guided khalifh.