This year began with ʿUmar b. al-Khaṭṭāb encouraging people to fight against the Iraqis. This was because news reached ʿUmar that during the Battle of al-Jisr, Abū ʿUbayd had been martyred, the Persians had united and agreed to enthrone Yazdegerd from their royal house, the people of al-Madāʾin in Iraq had broken their covenants, tormented the Muslims, and expelled them from among themselves. Upon this, ʿUmar sent instructions to his armies in Iraq to leave the city and camp in the surrounding areas.
The late Ibn Jarīr said: At the beginning of Muḥarram of this year, ʿUmar formed an army in Medina and set it in motion. The army encamped near the water of Sirār and established a camp. ʿUmar himself was leading this army to fight the Iraqis. He left ʿAlī as his deputy in Medina and took ʿUthmān b. ʿAffān and other leading figures among the Companions (ṣaḥāba) with him. Then, to consult about this decision, he convened a meeting of the Companions and sent word to ʿAlī, who came from Medina and attended. In the meeting, ʿUmar asked for their opinions. All expressed agreement with going to Iraq, except for ʿAbd al-Raḥmān b. ʿAwf, who said:
– O ʿUmar, I fear that if you are defeated and lose your strength, the Muslims in other lands will also be weakened. In my view,
you should return to Medina and send someone else to Iraq in your place.
This opinion of ʿAbd al-Raḥmān b. ʿAwf was approved by ʿUmar and the other members of the consultative assembly. Thereupon, ʿUmar asked ʿAbd al-Raḥmān b. ʿAwf:
– Whom do you suggest I send to Iraq?
– You have already found the man.
– Who is that?
– Saʿd b. Mālik al-Zuhrī, the one with the lion's claw.
ʿUmar approved of this suggestion and sent for Saʿd, appointing him as commander of the armies in Iraq. He gave him various counsels, saying:
– O Saʿd! Do not let it deceive or delude you when people say, "He is the uncle of the Messenger of God (peace be upon him) and one of his Companions (ṣaḥāba)." For there is no connection between anyone and Allah except through obedience to Him. All people are equal before Allah; He is their Lord and they are His servants. Yet, in well-being, they surpass one another, and this is attained only through obedience to Him. Whatever you saw the Messenger of God (peace be upon him) do from his mission until his death, do likewise. This is the command and my counsel to you. If you do not follow this advice and turn aside, your deeds will be rendered void and you will be among the losers." When ʿUmar was about to leave the camp and return to Medina, he said to Saʿd b. Mālik:
– You are on a straight path and have begun a good work. Be steadfast and patient in the face of afflictions you encounter. Always have taqwa (God-consciousness) of Allah. Know that taqwa is found in two things: obedience to Him and avoiding disobedience. Obedience to Him is to love the Hereafter and not love this world. Disobedience is to love this world and not love the Hereafter. There are certain truths in hearts that Allah brings forth; some are hidden, some manifest. The manifest truth is that, regarding the truth, the one who praises and the one who blames are the same. The hidden truth is that wisdom in a person's heart is revealed through the tongue and leads to people loving him. Do not neglect to desire that people love you, for even the prophets desired to be loved by people. If Allah loves a servant, He makes others love him; if He is angry with a servant, He makes others dislike him. However you are regarded among people, so will you be regarded with Allah."
It is said that Saʿd went to Iraq with an army of 4,000 men, 3,000 of whom were from Yemen and 1,000 from other regions. Some say the army numbered 6,000. ʿUmar accompanied them from the Sirār region as far as ʿAwwās. There, he addressed the people with the following speech:
"So that hearts may be revived, Allah has given you examples and spoken words for your sake. For hearts are dead within chests until Allah revives them. Whoever has knowledge should benefit from it. There are signs and glad tidings of justice. Its signs are modesty, generosity, gentleness, and kindness. Its glad tidings are mercy. Allah has opened a door for every matter and prepared a key for every door. The door of justice is taking heed, and its key is asceticism. Taking heed is to remember death and to prepare for it by giving away wealth. Asceticism is to take one's due from everyone who owes it and to be content with sustenance that suffices. If one is not content with sufficiency, nothing will make him rich. I am between you and Allah, but between me and Allah there is no one. Allah has appointed me so that you need not complain to Him about your condition. If you have a complaint, inform us. If you cannot reach us, present your complaint to our appointed officials to whom we have conveyed this command. We will take the right of the wronged from the wrongdoer, even by force."
ʿUmar returned to Medina with the Muslims who were with him, and Saʿd continued on the road to Iraq. Saʿd eventually reached the river of Zarūd, where he was close to Musannā b. Ḥāritha. Both longed to see each other. Musannā's wound from the Battle of al-Jisr (the Bridge) reopened, and he died—may Allah have mercy on him and be pleased with him. Before dying, he appointed Bashīr b. Ḥasāsiyya as his successor. When Saʿd heard of Musannā's death, he prayed for mercy for him and married his wife Salmā. When Saʿd arrived at the army's garrison, all commanders and local leaders came under his authority. ʿUmar sent him further reinforcements, so that at the Battle of al-Qādisiyya, he had an army of 30,000 under his command; some say 36,000. ʿUmar said: "By Allah, I will strike the Persian kings with the Arab kings," and sent Saʿd the following letter:
"Appoint commanders over the tribes and captains over every ten men, and order them to assemble at al-Qādisiyya."
Saʿd carried out this order, appointing captains over groups of ten and commanders over the tribes. He also, according to ʿUmar's instructions, appointed commanders over the reconnaissance, vanguard, right and left flanks, rearguard, infantry, and cavalry.
Sayf b. ʿUmar narrated from his teachers:
"ʿUmar appointed ʿAbd al-Raḥmān Rabiʿa al-Bāhilī al-Zannūn as judge and put him in charge of distributing the spoils. He assigned Salmān al-Fārisī to invite people to Islam and to preach and advise, and Ziyād b. Abī Sufyān as scribe."
It is said that there were only about 310 Companions (ṣaḥāba) in this army, more than seventy of whom had participated in the Battle of Badr. There were about 700 sons of Companions in the army—may Allah be pleased with them. ʿUmar sent Saʿd a letter urging him to move quickly to al-Qādisiyya. In the pre-Islamic period, al-Qādisiyya was the gateway to the Sasanian (Persian) Empire. In his letter, ʿUmar also instructed Saʿd: Let your army be between Ḥijr and the plain. Block all roads and passes leading to the Persians. Strike them first with a severe blow. Do not be intimidated by their numbers or equipment. They are a deceitful and scheming people. If you are patient, fight well, show ihsan (spiritual excellence), and fulfill trusts, I hope you will be victorious over them. Then they will be so shattered that they will never recover; they are fainthearted. If you are defeated, retreat to the region of Ḥijr. You are bolder and braver than they are; they are cowardly and ignorant. Eventually, Allah will grant you victory, and you will attack them again."
In his letter, ʿUmar also instructed Saʿd to engage in self-accounting, to exhort his soldiers, and to encourage them to have good intentions and sabr (patient endurance). He explained the reason: "For victory comes from Allah in proportion to a person's intention, and reward comes in proportion to one's expectation from Allah. Ask Allah for well-being. Say often: 'There is no power and no strength except with Allah, the Most High, the Most Great.' Inform me in detail of all your circumstances: where you camp, where the enemy is in relation to you. Send me such detailed letters that it is as if I am seeing you. Explain your situation clearly, have taqwa, be hopeful in Allah, and do not be negligent in anything. Know that Allah has promised the success of this matter, and this promise will certainly be fulfilled. Beware lest this matter causes you to be removed from command and replaced by others."
Saʿd wrote letters to ʿUmar describing the conditions of those regions and lands. Upon reading them, ʿUmar felt as if he were seeing those places. He also reported that the Persians had appointed Rustam and other commanders to fight them. In his letter, he wrote: "They seek to capture us, and we seek to capture them. Allah's command has come into effect, His judgment has been accepted, and we are content with His decree. We ask Allah for well-being in His good fate and destiny."
ʿUmar replied to him with the following letter:
"Your letter reached me. I read and understood it. When you meet your enemy and Allah grants you the opportunity to make them turn their backs and flee, it has been inspired to me that you will defeat them. Have no doubt about this. When you defeat them, do not relent until you have destroyed al-Madāʾin over their heads; that place, God willing, will be conquered."
ʿUmar began to make dua (supplication) especially for Saʿd and generally for all the Muslims.
When Saʿd reached Uzayb, the Muslims encountered a Persian military unit led by a commander named Shīrāzād b. ʿIrazuwayh. The Muslims captured a great deal of booty from them, thus gaining an advantageous position. Saʿd divided the spoils into five parts, sending one-fifth to the caliph and distributing four-fifths among the mujāhidūn (fighters). The mujāhidūn rejoiced at this and considered it a good omen. Saʿd also assigned a detachment to protect the women accompanying them, appointing Ghālib b. ʿAbd Allāh al-Laythī as their commander.