Allah T'ala says in the Holy Quran:
وَلَقَدْ خَلَقْنَاكُمْ ثُمَّ صَوَّرْنَاكُمْ ثُمَّ قُلْنَا لِلْمَلآئِكَةِ اسْجُدُواْ لآدَمَ فَسَجَدُواْ إِلاَّ إِبْلِيسَ لَمْ يَكُن مِّنَ السَّاجِدِينَ
قَالَ مَا مَنَعَكَ أَلاَّ تَسْجُدَ إِذْ أَمَرْتُكَ قَالَ أَنَاْ خَيْرٌ مِّنْهُ خَلَقْتَنِي مِن نَّارٍ وَخَلَقْتَهُ مِن طِينٍ
قَالَ فَاهْبِطْ مِنْهَا فَمَا يَكُونُ لَكَ أَن تَتَكَبَّرَ فِيهَا فَاخْرُجْ إِنَّكَ مِنَ الصَّاغِرِينَ
إِنَّهُ لاَ يُفْلِحُ الْمُجْرِمُونَ
The Qur'anic term falah (prosperity, success) used in the above verse (last part of verse 10:17) has been understood by some to signify such things as longevity, worldly prosperity and other worldly attainments. Under this false impression, they tend to believe that if a claimant to prophethood attains material prosperity and longevity or if his message is spread around, then he ought to be considered a genuine Prophet because he has indeed attained 'prosperity'. Had he been an impostor, it is argued, he would soon have been assassinated, or would have starved to death, and, in any case, his message would not have spread around. Such an absurd line of argument can only be pursued by those who are altogether ignorant of the concept of falah (prosperity) as envisaged in the Qur'an, who are unaware of God's law of respite regarding evil-doers, and who are altogether unappreciative of the special meaning in which the term has been employed in the present context.
In order to fully understand what is meant by saying that 'the guilty shall not prosper', a number of things ought to be borne in mind. In the first place, the Qur'anic statement that "the guilty shall not prosper' is not made with a view to providing a yardstick that might be applied by people so as to determine the truth or falsity of the claimants of prophethood. The verse does not seek to stress that all those who 'prosper' after claiming to be a Prophet are truly Prophets, and that those who do not prosper after making such a claim are not so. The point of emphasis here is altogether different. Here the Prophet (peace be on him) is being made to say that since he knows fully that those guilty of inventing lies against Allah could not prosper, he would not dare make any claim to prophethood if such a claim was false.
On the other hand, the Prophet (peace be on him) also knew that the unbelievers were guilty of rejecting the true signs of God and of declaring a true Prophet of God to be an impostor. In view of that monstrous guilt, it was quite apparent to the Prophet (peace be on him) that they would not prosper.
Moreover, the Qur'anic term falah (prosperity, success) has not been used in the limited sense of worldly success. Rather, it denotes that enduring success which admits of no failure regardless of whether one is able to achieve success in the present phase of one's existence or not. it is quite possible that someone who calls people to falsehood might enjoy life and nourish in a worldly sense, and he might even be able to attain a substantial following for his message. But this is not true prosperity or success; rather it constitutes total loss and failure. Contrarily, it is also possible that someone who calls people to the truth might be exposed to much persecution and be overwhelmed by pain and suffering. It is possible that even before he is able to create any significant following, he is continually subjected to persecution and torture. In the Qur'anic view, such an apparently tragic end constitutes the very zenith of such a person's success rather than his failure.
Moreover, it should be remembered that it has been amply elucidated in the Qur'an that God does not punish evil-doers instantly: that He rather grants them a fair opportunity to mend their ways. Not only that, if the evil-doers misuse the respite granted by God to perpetrate further wrongs, they are sometimes granted an even further respite. In fact, at times a variety of worldly favours are bestowed upon such evil-doers in order that the potential for wickedness inherent in them might be fully exposed by their actions, proving that they do indeed deserve a very severe punishment. Hence, if an impostor continues to enjoy periods of respite and if worldly favours are lavished upon him this should not in any way give rise to the notion that he is on the right path.
In the same way as God grants respite to other evil-doers. He also grants respite to impostors. There are no grounds whatsoever for believing that the respite granted to other evil-doers would not be granted to those impostors who lay false claim to prophethood. We may well call to mind that Satan himself has been granted a respite until Doomsday, It has never been indicated that although Satan is granted a free hand to misguide human beings, as soon as he throws up an impostor claiming prophethood such a venture is instantly nipped in the bud.
In order to refute the view expressed above it is possible that someone may refer to the following verse of the Qur'an: Now if he [i.e. Muhammad] would have made up, ascribed some sayings to Us, We would indeed have seized him by the right hand, and then indeed would have cut his life-vein (al-Haqqah 69: 44-6).
Even a little reflection makes it obvious that the verse in question does not contradict the view we have expressed above. For, what the present verse says relates to a principle which God follows in dealing with true Prophets. Were any such Prophet to falsely claim something to be a revelation from God, he would instantly be seized by God's wrath. To argue to the contrary that all those who are not seized by God's wrath are necessarily genuine Prophets is simply a logical fallacy devoid of any justification. For the threat of instant Divine wrath embodied in this verse is applicable only to true Prophets, and not to impostors who, like other evil-doers, are granted a respite.
This can be well understood if we bear in mind the disciplinary rules laid down by different governments for their officials. It is obvious that those rules are not enforced in respect of ordinary citizens. Were the latter to lay any false claim to being a government official, he would be subjected to the normal rules of the criminal code relating to the conviction of those who are guilty of fraud rather than to the disciplinary rules meant for government officials. Under this analogy, an impostor who claims to be a Prophet, would be dealt with by God along with other evil-doers who commit evil, and who, as we know, are not necessarily punished immediately.
In any case, as we have pointed out earlier, the verses quoted above were not revealed so as to provide the criterion to judge the truth of anyone who lays claim to prophethood. This verse should not be considered to mean that if a celestial hand stretches forth to cut off the life-vein of a claimant to prophethood, such a person is an impostor; and if that does not happen, he is a genuine Prophet. Such a weird criterion would have been needed only if no other means were available to judge the genuineness of a claimant to prophethood. But as things stand, a Prophet is known by his character, by his work, and by the contents of his message. (Tafheemul Quran)