After his surrender at Tustar, he was brought to Medina to be presented to the caliph. Before he and his escort entered the city, they arrayed him in all his finery, his brocade and cloth-of-gold robes and a crown studded with rubies. Then they led him through the streets so that everyone could see him. When they reached Umar's house, however, they found that he was not there, so they went to look for him in the mosque but could not find him there either. Finally they passed a group of boys playing in the street, who told them that the caliph was asleep in a corner of the mosque with his cloak folded under his head for a pillow.
When they returned to the mosque they found him as the boys had said. He had just received a delegation of visitors from Kūfa and, when they had left, he had simply put his head down for a nap. Apart from him there was no one in the mosque. They sat down a little way from him. Hurmuzān enquired where his guards and attendants were but was told he had none. "Then he must be a prophet," the Persian said. "No," his escort replied, "but he does the things prophets do." Meanwhile more people gathered round and the noise woke Umar up. He sat up and saw the Persian and the escort asked him to talk to the "king of Ahvaz." Umar refused as long as he was wearing all his finery, and only when the prisoner had been stripped as far as decency allowed and reclad in a coarse robe did the interrogation begin.
Umar asked Hurmuzān what he thought about the recent turn of events, to which the Persian replied that in the old days God was not on the side of the Persians or the Arabs and the Persians were in the ascendancy, but now God was favoring the Arabs and they had won. Umar replied that the real reason was that the Persians had previously been united while the Arabs had not. Umar was inclined to execute him in revenge for the Muslims he had slain. Hurmuzān asked for some water, and when it was given to him he said he was afraid he would be killed while he was drinking. The caliph replied that he would not be killed before he had drunk the water, whereupon Hurmuzān allowed his hands to tremble and the water was spilled. When Umar again threatened to kill him, the Persian said that he had already been given immunity; after all, he had not drunk the water. Umar was furious, but the assembled company agreed that Hurmuzān was right. In the end, he was converted to Islam, allowed to live in Medina and given a substantial pension.
The story of Hurmuzān's trick is probably a folk motif grafted on to historical events, but it serves its purpose to illustrate the contrast between Persian pride and luxury and Muslim simplicity; the honesty of the Muslims and the integration of elements of the Persian elite into the Muslim hierarchy.
In E.J. Brill's First Encyclopaedia of Islam, 1913-1936, al-Hurzumān, described as the King of Susiana,
"...succeeded as saving his life by his cunning but only on condition that he adopted Islām. He was able to be useful to the Caliph in various ways on account of his knowledge of Persian affairs. But when 'Omar was murdered in 23 = 644 by a Persian Christian, al-Hurmuzān, probably without reason, was suspected of being an accomplice and killed by 'Ubaid Allāh, son of the Caliph." (p. 338)
Photo credit: Panoramio/shushtari