In this year, a letter arrived from the Abbasid imam, Ibrahim b. Muhammad, commanding Abu Muslim al-Khurasani to set out from Khurasan. Abu Muslim then set off with seventy representatives. In every city they passed through, the people would inevitably ask where they were going, and they would reply that they were on pilgrimage (hajj). When Abu Muslim perceived an inclination towards them in certain individuals, he invited them to strive for their cause. These individuals responded to his invitation. While on the road, a second letter from the Abbasid imam Ibrahim reached Abu Muslim. The letter stated: "I have sent you the banner of victory. Return to Khurasan and proclaim your call." Abu Muslim then ordered Kahtaba b. Shabib to go to Imam Ibrahim with the goods and gifts he had, and to meet him during the pilgrimage season. Abu Muslim, having received Imam Ibrahim's letter, returned to Khurasan. He entered the city during the days of Ramadan. He presented the letter to Sulayman b. Kasir. The letter stated: "Proclaim your call and do not delay." They appointed Abu Muslim al-Khurasani as the Abbasid envoy for their cause, and Abu Muslim dispatched propagandists to various regions of Khurasan.
He sent them out.
At this time, the governor of Khurasan, Nasr b. Sayyar, was occupied with killing the Kirmani and settling the matter of Shayban b. Salama al-Haruri. His position was so strong that his men would greet him among many Kharijite factions with the greeting reserved for caliphs.
When Abu Muslim emerged, people flocked to him from all directions. In a single day, the people of sixty villages turned to him. He resided in Khurasan for forty-two days, conquering many cities and towns. Five days before the end of Ramadan in the year 129 AH, on a Thursday night, Abu Muslim affixed the banner called "Shadow," sent to him by Imam Ibrahim, to the tip of a spear fourteen cubits long. He also affixed the banner called "Cloud," also sent by Ibrahim, to the tip of a spear thirteen cubits long. Both banners were black in color. While doing all this, Abu Muslim al-Khurasani recited the following verse:
"Permission [to fight] has been given to those who are being fought, because they were wronged. And indeed, Allah is competent to grant them victory." (al-Hajj 22:39)
Abu Muslim, Sulayman b. Kasir, and those who supported them in this cause wore black garments. The black garment became their symbol. That night, they lit a great fire. Through this fire, they called the surrounding people to themselves. This became a sign among them. Thus, they gathered together. The reason one of the banners was named "Cloud" was that just as a cloud covers all parts of the earth, so too would the Abbasids cover the whole world with their call. The reason the other banner was named "Shadow" was that just as there is shadow everywhere on earth, so too would the Abbasids be present everywhere on earth.
People turned to Abu Muslim from all directions. Thus, his army grew.
Abu Muslim ordered Sulayman b. Kasir to lead the Eid prayer at Inzara Dayram on the day of Eid al-Fitr. He had a pulpit prepared for him and commanded him to oppose the Umayyads and act according to the sunnah. The announcement was made with the phrase "as-salātu jāmiʿa" (the prayer is gathering). The call to prayer (adhan) and the commencement (iqama) were not performed. The Umayyads would perform both the adhan and iqama for the Eid prayer. The prayer was led before the sermon, with six takbirs before the Fatiha in the first unit, and five takbirs in the second unit, instead of the usual four and three. In this way, they opposed the Umayyads. The sermon began with dhikr (remembrance of God) and takbir (proclamation of God's greatness). He completed the sermon by reciting a Qur'anic verse. After the congregation dispersed from the Eid prayer, they ate the Eid meal prepared by Abu Muslim.
Abu Muslim wrote a letter to Nasr b. Sayyar. In the letter, he wrote his own name before Nasr's. The letter read:
"In the name of Allah, the Most Gracious, the Most Merciful.
Now then, Allah has changed some peoples in His Book and has said: 'And they swore by Allah their strongest oaths that if a warner came to them, they would be more guided than [any] one of the [previous] nations; but when a warner came to them, it did not increase them except in aversion. [They behaved] arrogantly upon the earth and plotted evil; but the evil plot does not encompass except its own people. Then do they await except the way of the former peoples? But you will never find in the way of Allah any change, and you will never find in the way of Allah any alteration.' (al-Fatir 35:42-43)
It weighed heavily on Nasr that Abu Muslim had written his own name first in the letter. He thought long and hard and said: "This letter must be answered."
Ibn Jarir said: Nasr b. Sayyar sent a large cavalry unit to fight Abu Muslim. This incident occurred eighteen months after Abu Muslim's emergence. Abu Muslim sent Malik b. Haytham al-Khuza'i against this cavalry force. The two sides confronted each other. Malik asked them to accept the rule of the Prophet's family, but they refused. They stood in ranks from morning until afternoon. Reinforcements arrived for Malik, strengthening him, and he defeated them. This was the first battle between the Umayyad and Abbasid armies.
In this year, Hazim b. Khuzayma captured Marw-i Ruz. He killed Bishr b. Ja'far al-Sa'di, the governor appointed there by Nasr b. Sayyar. He sent the news of the conquest to Abu Muslim.
At that time, Abu Muslim was a young man. The Abbasid imam Ibrahim had chosen him to strengthen their propaganda and call, for Abu Muslim was bold, sharp-witted, and perceptive. He was originally from the Sawad of Kufa. He had been the slave of Idris b. Maqil al-Ijli. An Abbasid propagandist had purchased him for 400 dirhams. Later, Muhammad b. Ali bought him, and thus he came under the protection of the Abbasids. Imam Ibrahim married him to the daughter of Abu al-Najm Isma'il b. Imran, giving her dowry. He also sent a letter to the Abbasid propagandists and callers in Khurasan and Iraq, instructing them to obey and follow Abu Muslim. The previous year, the Abbasid propagandists had not obeyed Abu Muslim because of his youth. This year, Imam Ibrahim reaffirmed his command in another letter, instructing the propagandists to obey Abu Muslim. This was beneficial for both Abu Muslim and the Abbasid propagandists and callers. "Indeed, the command of Allah will be fulfilled." (al-Ahzab 33:38)
As Abu Muslim's power spread in Khurasan, the Arab tribes there made an agreement among themselves to fight him. Kirmani and Shayban were not forced into this agreement, as both had rebelled against Nasr and Abu Muslim. Abu Muslim himself was opposed to Nasr. Thus, Kirmani and Shayban were left in their respective positions.
Nevertheless, Nasr was calling on the people to depose Marwan al-Himar from the caliphate. Nasr asked Sayhan to assist him in his war against Abu Muslim or to stay away until he had finished the matter. He stated that after killing Abu Muslim, he would resume settling scores. Shayban responded positively to this request. When Abu Muslim learned of this, he informed Kirmani of what had transpired. Kirmani, in turn, reproached Shayban for his stance and called on him to break his agreement with Nasr, preventing him from assisting Nasr.
Abu Muslim sent Nadr b. Na'im against Herat. Nadr took the city from its governor, Isa b. Uqayl al-Laysi, and reported this to Abu Muslim in a letter. Isa, the governor of Herat, fled to Nasr. Later, Shayban made a non-aggression pact, promising not to attack Nasr for a year. This was due to Kirmani's pressure. Kirmani informed Abu Muslim that he would support him in his war against Nasr. Abu Muslim then went to Kirmani, honored him, and the two agreed and allied to fight and oppose Nasr.
Abu Muslim's dominion spread over a wide area. His army grew, and his forces increased. Like a ruler, he appointed officials over security forces, police and gendarmerie, the postal service, the diwan, and similar offices. One of the naqibs, Qasim b. Mujashi' al-Tamimi, was appointed head of the justice administration. This man also led the prayers for Abu Muslim, recounted stories, praised the virtues of the Hashimites, and criticized the Umayyads. Abu Muslim went to the town of Balin, which was located in a low place, fearing that Nasr b. Sayyar would cut off the water flowing to that area. He went to Balin on the 6th of Dhu al-Hijjah that year. The Eid prayer was led by Qasim b. Mujashi'. Nasr b. Sayyar, meanwhile, marched towards Abu Muslim with his large army, intending to fight him. He left deputies in his place. When discussing the events of the year 130 AH, we will recount these battles between Abu Muslim and Nasr b. Sayyar.