During the time of Prophet Muhammad (pbuh) the authenticity and credibility of Islam, the Quran and the Prophet himself laid in the hands of one man at a particular point.
Abu Lahab did not believe in Islam.
When Abu Lahab was still well and alive, a short chapter of the Quran was revealed to the Prophet. The chapter said that Abu Lahab will die a non-muslim and will go to hell for not believing in the Oneness of God.
"The power of Abu Lahab will perish, and he will perish. His wealth and gains will not exempt him. He will be plunged in flaming Fire, And his wife, the wood-carrier, Will have upon her neck a halter of palm-fibre." Al Quran Chapter 111.
Abu Lahab lived for many years after this prophecy was revealed. He could have destroyed the credibility of Islam and the Prophet simply by pretending to convert. But he didn't....Allah knows all. It is the will of God that is revealed in the chapter above and Abu Lahab, nor anyone in the world can go against the will of God.