Patricia Crone’s book Hagarism refers to the History of Bishop Sebeos, translated here. Crone says, “For this we have to turn to the earliest connected account of the career of the Prophet, that given in an Armenian chronicle written in the 660s and ascribed to Bishop Sebeos. The story begins with the exodus of Jewish refugees from Edessa following its recovery by Heraclius from the Persians towards 628:” She then quotes part of the following section about the rise of Islam:
I shall discuss the [line of the] son of Abraham: not the one [born] of a free [woman], but the one born of a serving maid, about whom the quotation from Scripture was fully and truthfully fulfilled, “His hands will be at everyone, and everyone will have their hands at him [Genesis 16. 11,12].”
Twelve peoples [representing] all the tribes of the Jews assembled at the city of Edessa. When they saw that the Iranian troops had departed and left the city in peace, they  closed the gates and fortified themselves. They refused entry to troops of the Roman lordship. Thus Heraclius, emperor of the Byzantines, gave the order to besiege it. When [the Jews] realized that they could not militarily resist him, they promised to make peace. Opening the city gates, they went before him, and [Heraclius] ordered that they should go and stay in their own place. So they departed, taking the road through the desert to Tachkastan to the sons of Ishmael. [The Jews] called [the Arabs] to their aid and familiarized them with the relationship they had through the books of the [Old] Testament. Although [the Arabs] were convinced of their close relationship, they were unable to get a consensus from their multitude, for they were divided from each other by religion. In that period a certain one of them, a man of the sons of Ishmael named Muhammad, a merchant, became prominent. A sermon about the Way of Truth, supposedly at God’s command, was revealed to them, and [Muhammad] taught them to recognize the God of Abraham, especially since he was informed and knowledgeable about Mosaic history. Because the command had [g104] come from On High, he ordered them all to assemble together and to unite in faith. Abandoning the reverence of vain things, they turned toward the living God, who had appeared to their father, Abraham. Muhammad legislated that they were not to  eat carrion, not to drink wine, not to speak falsehoods, and not to commit adultery. He said: “God promised that country to Abraham and to his son after him, for eternity. And what had been promised was fulfilled during that time when [God] loved Israel. Now, however, you are the sons of Abraham, and God shall fulfill the promise made to Abraham and his son on you. Only love the God of Abraham, and go and take the country which God gave to your father, Abraham. No one can successfully resist you in war, since God is with you.”
Then all of them assembled together, from Havilah to Shur, which is opposite Egypt [The text is corrupt here. The citation is from Genesis 25.18], and they set out from the P’arhan desert [being] twelve tribes [moving] in the order [of precedence] of the Houses of the patriarchs of their tribe. They were divided into 12,000 men, of which the sons of Israel were in their own tribes, 1,000 to a tribe, to lead them to the country of Israel. They travelled army by army in the order [of precedence] of each patriarchy: Nebaioth, Kedar, Adbeel, Mibsam, Mishma, Dumah, Massa, Hadad, Tema, Jetur, Naphish and Kedemah [Genesis 25. 13-16]. These are the peoples of Ishmael. They reached Moabite Rabbath, at the borders of  Ruben’s [land]. The Byzantine army was encamped in Arabia. [The Arabs] fell upon them suddenly, struck them with the sword and put to flight emperor Heraclius’ brother, Theodosius. Then they turned and encamped in Arabia.
The author of Sebeos later writes: “We heard this [account] from men [who had returned] from captivity in Xuzhastan Tachkastan, who themselves had been eye-witnesses to the events described and narrated them to us.” Crone notes “The chronicle ends in 661 and was clearly written by a contemporary; the question of its true authorship and title does not concern us. The account of the Arab conquests is stated to be based on testimony of eyewitnesses who had been held prisoner by the Arabs (p. 102).”
The differences of this account of Islamic origins and the version we here from Islam are obvious.
Post I here.