After the battle of Jalaula, the Persian forces scattered in various pockets. One of such pockets was Masabzan. As Hashim b. Utba was returning from Jalaula to Madain, he was informed in the way by his army scouts that some of the Persian forces which had escaped from Jalaula had assembled in the territory of Masabzan at the base of the hills under the command of Azeen the son of Hormuzan. When Hashim reached Madain, he communicated this information to Sa'ad. Sa'ad in turn wrote to Umar and sought his instructions, particularly when he had ordered that there should be no further advance in Persia.
Umar wrote to say that while he was against any advance into Persia proper, he was not against the liquidation of Persian pockets in Iraq which might be a threat to Muslim dominions. We accordingly desire that in the interests of the safety of Iraq, an expedition should be led to Masabzan which should be occupied and cleared of the Persian forces. Umar appointed Zarrar b. Khattab of the tribe of Maharab to the chief command of the force to be led against Masabzan, Ibn Hazil Asadi was appointed as the commander of the advance guard. Abdullah bin Wahb Rabbi was appointed to the command of the right wing, and Musarab al-Ajaali was appointed as the commander of the left wing.
Some time in January 638 AD, a Muslim force under the command of Zarrar marched to Masabzan. At Hindaf the two forces clashed. The Persians under Azeen fought desperately, and in spite of heavy pressure of the Muslims held their ground. Azeen directed the operations from an elevated place in the rear of the Persian army Zarrar withdrew the Muslim army to some distance, and the Persians thinking that they had won the day rushed forward The Muslim army counter charged and the Persians could not withstand the charge. In the meantime some Muslim warriors managed to reach the camp of Azeen and captured him alive. With the capture of Azeen the war was over, and whatever remained of the Persian army took to flight.
From Hindaf the Muslim army marched to Sirwan. No resistance was offered. The city had been evacuated and the Persian army as well as the citizens of Sirwan had fled to the hills. Zarrar occupied Sirwan and established his headquarters there.
He announced general amnesty, and asked the people to return to their homes The offer was availed of and the citizens returned to their homes. A peace treaty was drawn up and the inhabitants agreed to pay Jizya. Considerable booty was obtained which was distributed according to the usual formula.
After the restoration of peace, Zarrar stayed in Sirwan as the Governor. He organised the administration, appointed Muslim Officers in the districts, and collected taxes. Later when Kufa was founded as the capital of Iraq, Zarrar moved to Kufa leaving Ibn Hazil Asadi as his successor in Masabzan.