Almighty Allah declared: Those (i.e., believers) unto whom the people (hypocrites) said: "Verily, the people (pagans) have gathered against you (a great army), therefore, fear them." But it (only) increased them in Faith, and they said: 'Allah (Alone) is Sufficient for us, and He is the Best Disposer of affairs (for us)."

So they returned with Grace and Bounty from Allah. No harm touched them; and they followed the good Pleasure of Allah. And Allah is the Owner of Great Bounty. It is only Satan that suggests to you the fear of his Auliya supporters and friends (polytheists, disbelievers in the Oneness of Allah and in His Messenger Muhammad), so fear them not, but fear Me, if you are (true) believers." Surah 3: 173-175

The People's Reaction to the Fire
The throng, the chiefs, and the priests sat watching the fire from a distance. It was burning their faces and nearly suffocating them. It kept burning for such a long time that the disbelievers thought it would never be extinguished.
When it did burn out, they were greatly amazed to find Abraham coming out of the pit untouched by the fire. Their faces were black from the smoke, but his was bright with the light and grace of Allah. The raging fire had become cool for Abraham and had only charred the ropes which held him. He walked out of the fire as if he were walking out of a garden. Cries of astonishment were heard from the heathens. They wanted to harm him, but We made them the worst losers. Surah 21:70
This miracle shamed the tyrants, but it did not cool the flame of anger in their hearts. However, after this event many of the people followed Abraham, although some kept their belief a secret for fear of harm or death at the hands of the rulers.

Abraham's Dialogue with Namrud
Abraham had established a definite reasoning against idolators. Nothing was left for him except to reason against the people who proclaimed themselves gods.
When the king, Namrud, heard of Abraham's safe exit from the fire he became very angry. He feared that the status of godhead he had proclaimed for himself was now challenged by an ordinary human being. He summoned Abraham to the palace and held a dialogue with him, which Allah the Almighty recounted: Have you not thought about him who disputed with Abraham about his Lord (Allah), because Allah had given him the kingdom? When Abraham said (to him). 'My Lord (Allah) is He Who gives life and causes death." He said: "I give life and cause death." Abraham said: "Verily! Allah causes the sun to rise from the east; then cause it you to rise from the west." So the disbeliever was utterly defeated. And Allah guides not the people who are Zalimeen (wrongdoers, etc.). Surah 2: 258