Muhammad Continues Preaching to the Quraish
While the followers of the Prophet sought safety in foreign lands against the persecution of their people, he continued his warnings to the Quraish more strenuously than ever. Again they came to him with offers of riches and honor, which he firmly and utterly refused. But they mocked at him and urged him for miracles to prove his mission. He used to answer: "Allah has not sent me to work wonders; He has sent me to preach to you."
Thus disclaiming all power of wonder-working, the Prophet ever rested the truth of his divine mission upon his wise teachings. He addressed himself to the inner consciousness of man, to his common sense and to his own better judgment. Say (0 Muhammad): 'lam only a human being like you. It is inspired in me that your Ilah (God) is One Ilah (God - Allah), therefore take the Straight Path to Him (with true Faith - Islamic Monotheism) and obedience to Him, and seek forgiveness of Him. And woe to Al-Mushrikeen: polytheists, pagans, idolaters, and disbelievers in the Oneness of Allah etc., those who worship others along with Allah or set up rivals or partners to Allah etc.. Surah 41: 6

Muhammad is Asked for a Sign
Despite all the exhortations of the Prophet, the Quraish persisted in asking him for a sign. They insisted that unless some sign be sent down to him from his Lord, they would not believe. The disbelievers used to ask: "Why has Muhammad not been sent with miracles like previous prophets?" The Prophet replied: "Because miracles had proved inadequate to convince. Noah was sent with signs, and with what effect? Where was the lost tribe of Thamud? They had refused to receive the preaching of the Prophet Salih, unless he showed them a sign and caused the rock to bring forth a living camel. He did what they asked. In scorn they cut the camel's feet and then, daring the prophet to fulfill his threats of judgment, were found dead in their beds the next morning, stricken by the angel of the Lord."
There are some seventeen places in the Qur'an, in which the Prophet Muhammad is challenged to work a sign, and he answers them all to the same or similar effect: Allah has the power of working miracles, and had not been believed; there were greater miracles in nature than any which could be wrought outside of it; and the Quran itself was a great, everlasting miracle. The Qur'an, the Prophet used to assert to the disbelievers, is a book of blessings which is a warning for the whole world; it is a complete guidance and explains everything necessary; it is a reminder of what is imprinted on human nature and is free from every discrepancy and from error and falsehood. It is a book of true guidance and a light to all.