Adh-Dhahabi related that when Al-Aswad Al-Ansi openly claimed to be a Prophet, Abu Muslim Al-Khawlaani spoke out against him. Al-Aswad ordered his men to capture Abu Muslim, and to prepare a huge fire for him. When that huge fire was ignited in a pit, Al-Aswad threw Abu Muslim inside.
Miraculously, however, the fire did not harm Abu Muslim in the least, which was reminiscent of how Prophet Ibraheem (as) was not harmed by a fire into which he had been thrown.
At any rate, Al-Aswad said, “If you do not banish Abu Muslim from this land, he will turn your followers against you.”
Realising that his advisors were right and that he would not be able to harm Abu Muslim physically, Al-Aswad ordered Abu Muslim to travel away from the region immediately.
Wanting the company of the righteous people, Abu Muslim Al-Khawlaani was probably more than happy to comply, and so he headed towards the city of the Messenger of Allaah (saw), Al-Madeenah Al-Munawwarah. Upon arriving in Madeenah, Abu Muslim made his camel kneel down on the ground, after which he proceeded to enter the Prophet’s Masjid.
‘Umar, who at the time was inside the Masjid, stood up to meet the stranger who had just entered and asked, “Where are you from?”
“From Yemen,” replied Abu Muslim.
“And what do you know about the man that the “Liar” tried to burn with fire?” asked ‘Umar.
That is ‘Abdullaah Ibn Thuwab, ” replied Abu Muslim.
Looking keenly at Abu Muslim, ‘Umar had a string feeling about him, as if he knew something about the character of the stranger, even though he had never previously seen him. So ‘Umar asked him, “I ask you by Allaah, are you him?”
“Yes,” replied Abu Musim.
‘Umar said, “All praise is for Allaah, Who has not caused me to die before showing me the person from the nation of Muhammad for whom was done the same that was done for Ibraheem Al-Khaleel.”
[Siyaar A’laam An-Nubulaa 4/8]