Allah sent (the Prophet) Muhammad and said:-- 'Say, No wage do I ask of you for this (Qur'an) nor am I one of the pretenders (i.e. a person who pretends things which do not exist). (38.68) When Allah's Apostle saw Quraish standing against him, he said, "O Allah! Help me against them by afflicting them with seven years of famine similar to the seven years (of famine) of Joseph. So they were afflicted with a year of drought that destroyed everything, and they ate bones and hides. (One of them said), "And they ate hides and dead animals, and (it seemed to them that) something like smoke was coming out of the earth. So Abu Sufyan came to the Prophet and said, "O Muhammad! Your people are on the verge of destruction! Please invoke Allah to relieve them." So the Prophet invoked Allah for them (and the famine disappeared). He said to them. "You will revert (to heathenism) after that." 'Abdullah then recited: 'Then watch you for the Day that the sky will bring forth a kind of smoke plainly visible.......but truly you will revert (to disbelief).' He added, "Will the punishment be removed from them in the Hereafter? The smoke and the grasp and the Al-Lizam have all passed." One of the sub-narrater said, "The splitting of the moon." And another said, "The defeat of the Romans (has passed)."
Sahih al-Bukhari, Vol. 6, Book of Prophetic Commentary on the Qur'an, Hadith 349
Sahih al-Bukhari, Book of Prophetic Commentary on the Qur'an, Hadith 349