There were few Jews in Mecca when Muhammad first announced he was to be obeyed as the Prophet of Allah, and his early efforts were directed towards the pagan Quraysh. He preached quietly for three years, and then became more public and confrontational, stating that he was a "plain warner of a coming severe punishment". The short blunt Meccan suras of the Quran mention hell 146 times, lucidly describing the parched skins and scalding water awaiting those who did not follow Muhammad.
Muhammad often repeated the stories from the Torah of Abraham, Joseph, and Moses, but with a distinctly different emphasis. In Muhammad's version, Allah had been prepared to destroy each of those civilizations unless they obeyed the prophets. God didn't just tell Abraham to leave Iraq and go to Canaan for a great blessing as recorded in Genesis, he was about to wipe out Abraham's people. This was the backdrop for Muhammad's main message, which was that Allah would likewise destroy everyone who did not accept him as the final and greatest prophet.
The Quraysh did not take kindly to Muhammad's warnings of divine judgment. They were not familiar with the Torah but Medina, a city 250 miles to the north, was about 50 percent Jewish. The rabbis there had long threatened enemies who robbed them that a prophet would come to set things straight. The Quraysh sent a delegation to Medina to inquire of the rabbis whether Muhammad might be this prophet. The rabbis told them to ask Muhammd three specific questions that would determine his validity. Suras 17 and 18 of the Quran give Muhammad's answer to the questions.
Looking back from a historical perspective, it is doubtful the rabbis really believed a non-Jewish Arab Muslim would be their anticipated prophet, but Muhammad thought they did. He began to focus his attention on them and stated that the Quran was the answer to all their questions. He also claimed to be taken to heaven on a night journey where he was accorded by Allah a status higher than all their prophets.
When some non-Jewish Medinans heard Muhammad's message at an annual fair outside Mecca, they converted to Islam. Returning to Medina, they gave good reports of Muhammad. They returned to the fair the following year, and invited Muhammad to their city. Most of them were from the Aus and the Khazraj tribes. The Aus were aligned with the Jewish tribes of Qurayza and Al-Nadir, and the Khazraj with the Jewish tribe of Qaynuqa. There were tribal conflicts in Medina, and they thought that Muhammad could come and mediate the differences. Muhammad saw this as an opportunity for expansion, and accepted the invitation. The year was 622 A.D., year one of the Muslim calendar, and Muhammad and his followers immigrated to Medina with great expectations of what the future would hold.