When Saʿd reached al-ʿUdhaib (1), a Persian force led by Shirzad ibn Azaduyah (2) intercepted the Muslims. The Muslims captured a large amount of what he was carrying and dealt them a serious blow. Saʿd set aside the statutory one-fifth of the booty and distributed the remaining four-fifths among the troops. The soldiers rejoiced, took heart, and regarded it as a good omen. Saʿd then detached a separate detachment to guard the women who were with the army, appointing Ghalib ibn ʿAbd Allah al-Laythi as its commander.

Section: The Expedition of al-Qadisiyyah

Saʿd resumed the march and encamped at al-Qadisiyyah. He sent out scouting parties in all directions and remained there for a month without seeing a single Persian. He wrote to ʿUmar to report this, while those detachments kept bringing in supplies from every quarter. The peasantry of Persia, from the farthest edges of their land, flocked to Yazdegerd, complaining of the plunder and captivity they were suffering at the Muslims’ hands. They said, “If you do not come to our aid, we will hand over what we possess and surrender our fortresses to them.”

The Persians agreed that Rustam should be sent against the Muslims. Yazdegerd summoned him, appointed him commander of the army, but Rustam asked to be excused, saying, “This is not sound strategy: sending wave after wave of troops is harder on the Arabs than letting them defeat one massive army all at once.” The king would not relent, so Rustam prepared to set out (3).

Meanwhile, Saʿd sent a reconnaissance party toward al-Hirah (and toward Ṣulūbā). News came back that the king had put Rustam ibn al-Farrukhzād the Armenian in charge of the war and had reinforced him with additional forces.

Saʿd wrote to ʿUmar about this, and ʿUmar replied: “Let not what you hear about them distress you (4), nor what they may bring against you. Seek Allah’s help, rely on Him, and send to Rustam men of insight, sound judgment, and fortitude to invite him to Islam, for Allah will make their invitation a source of weakness for the enemy and a victory (5) for you. Write to me every day.”

When Rustam drew near with his army and camped at Sābāṭ (6), Saʿd wrote to ʿUmar: “Rustam has camped at Sābāṭ. He has mustered horses and elephants and is advancing upon us with them. Nothing occupies me more, or is more often on my tongue, than my wish to rely on Allah and seek His aid (7).”

Rustam then organized his forces: he placed Jalīnūs over the vanguard, forty thousand strong; al-Hurmuzān over the right wing; Mihrān ibn Bahrām—sixty thousand strong—over the left; and Bandurān over the rear guard with twenty thousand men. According to Saif (8) and others, the total force numbered eighty thousand.