The following tales is told of the Persian theologian and Sufi Sahl al-Tustari, who is said to have engaged in almost perpetual zikar, and was one of the early teachers of the mystic and martyr Mansur al Hallaj. (To learn about how he began his life of zikar, see this story.)
One day, not long before he left this world, Sahl was sitting with his companions where a certain man passed by. Seeing him, Sahl said, “This man holds a secret,” but when the students looked, the man had gone.
After Sahl’s death, it happened that one of his disciples was sitting by his grave when the same man came by.
”Sir,” the disciple addressed him, “the shaikh who lies in this tomb once said that you hold a secret. By that One who has vouchsafed this secret to you, I ask you to make me a demonstration.”
The man pointed to Sahl’s grave. “Sahl, speak!” he said.
A voice spoke loudly within the tomb. “There is no god but God alone, Who has no partner.”
”They say,” said the man, ”that whosoever believes that there is no god but God, there is no darkness for him in the grave. Is that true or not?”
Sahl cried from the grave, ”It is true!”