Sahl Khorasani approached Imam Sadiq (a.s.) and complained:
“Why is it that in spite of the truth being on your side, you do not stage an uprising? At the present time, there are one hundred thousand of your Shiites, who upon your orders, would immediately unsheathe their swords for battle.”
The Imam (a.s.), with the intention of giving him a practical answer, ordered the furnace to be lighted. He then instructed Sahl to jump into the flames.
Sahl said, “O’ My Master! May God shower you with His grace and favours! Do not place me in the fire. I take back my words and request you to withdraw your instruction too.”
Meanwhile, one of the sincere companions of the Imam (a.s.), by the name of Haroon Makki, happened to arrive. Just as he entered, the Imam (a.s.) told him to take off his shoes and walk into the hot furnace. As soon as Haroon heard the Imam’s (a.s.) order, he entered the furnace and sat within the flames.
The Imam (a.s.) then turned to Sahl and started to brief him about the circumstances prevailing in Khorasan, as if he had been there to witness the events taking place.
After a while, he said to Sahl, “Get up and have a look inside the furnace.”
When Sahl peered into the furnace, he saw Haroon sitting cross-legged and unharmed inside, surrounded by the fiery flames.
“How many individuals like this one exist in Khorasan?” the Imam (a.s.) questioned Sahl.
“ By Allah! Not a single person like Haroon Makki exists in Khorasan,” replied Sahl.
The Imam (a.s.) then explained, “I shall not stage an uprising when I do not have even five sincere companions. (And do remember) we are very well aware as to when we should stage an uprising.”( Hikaayat-ha-e-Shanidani, vol. 4, pg. 65; Safinah al-Bihaar, vol. 2, pg. 714.)