He went on to relate:
He then stripped the Turk of his neck-torque and remained standing where the man had fallen. A second Turk came out, likewise wearing a torque and carrying a drum, and began to beat upon it. Al-Ahnaf stepped forward, slew him as well, took his torque, and again stood in his place. A third emerged—he, too, was killed and his torque taken. Al-Ahnaf then hurried back to his forces, and not a single Turk had any inkling of what had taken place.
It was the Turks’ custom never to leave their bivouac until three of their elders had come out ahead of the army: the first beating his drum, then the second, then the third; only after the third did the main host advance. So when the Turks came out that night (1) after the third elder, they found their mounted vanguard already bloodied. King Khāqān took it as a sinister omen and grew anxious. He said to his army, ‘We have stayed here too long, and these men have suffered (2) losses such as we have never known. There is no good for us in fighting these people. Let us withdraw.’ They therefore returned to their own country.
The Muslims waited the whole day for them to pour out of the mountain passes, but saw none of them. News then reached the Muslims that the enemy had gone back to their lands. (While Khāqān was facing al-Ahnaf in battle, Yazdajird had gone to Marw al-Shāhijān, laid siege to it, and to Ḥāritha ibn al-Nuʿmān (3) who was inside, dug up the treasury he had buried there, and then returned; Khāqān remained in Balkh awaiting his arrival.)
The Muslims said to al-Ahnaf, ‘What do you think about pursuing them?’ He replied, ‘Stay where you are and leave them be.’ Al-Ahnaf judged correctly, for the hadith states, ‘Leave the Turks so long as they leave you.’ (4) Allah—exalted is He—also says: ‘Allah repelled those who disbelieved in their rage; they gained no advantage. Allah sufficed the believers in fighting, and Allah is All-Powerful, Almighty.’ [al-Aḥzāb 33:25]
Thus Kisrā returned a loser, his thirst for vengeance unquenched, having gained nothing and secured no victory as he had imagined. Those from whom he hoped for aid deserted him, kept their distance, and disowned him at the very moment he most needed them. He remained wavering, belonging neither to these nor to those: ‘Whomever Allah leads astray, you will never find a way for him.’ [al-Nisāʾ 4:88] He was at a loss—what should he do, and where should he go?
Some of the wise among his people advised him when he said, ‘I have resolved to go to the land of China or to stay with Khāqān in his country.’ They replied, ‘We think you should come to terms with these people, for they possess covenant-keeping and a religion to which they hold. We could settle in some of these provinces as their neighbors (5); they would be better for us than others.’ Kisrā rejected their counsel.
He then sent to the King of China, appealing for help and seeking reinforcement. The Chinese ruler questioned the envoy about the description of these people who had conquered so many lands and subdued the necks of men. The envoy described their appearance, how they rode horses and camels, what they did, and how they prayed.
The king wrote back to Yazdajird: ‘Nothing prevents me from dispatching to you an army whose vanguard would be in Marw and whose rear would be in China, save my uncertainty about the duty that truly rests upon me (6); but these people…’