After that, the fact that the Qur'an was from Allah and that it was His Word was driven home with an open argument by saying: فَقَدْ لَبِثْتُ فِيكُمْ عُمُرًا مِّن قَبْلِهِ (Then I have lived among you for years before it). In effect, he was saying, ` just think for a moment. Is it not that, much before the revelation of the Qur'an, I have spent a long period of forty years of my life among you? During this period, you have never heard me composing and reciting poetry or writing essays in prose. Had I been proficient in saying something like this Word of Allah, I would have naturally said at least some of it during this period of forty years. In addition to that, you have a direct experience of my character and conduct, particularly of my truth and honesty, during these long forty years of my life among you. You know that I have never lied then. How and why would I start lying now after all those forty years?' This clearly proves that the Holy Prophet ﷺ is true and trustworthy. Whatever there is in the Qur'an is the Word of Allah Ta` ala and has come from Him.
Important Note
No doubt, this argument of the Qur'an provides a perfect proof of its veracity as the Word of Allah. But, it has also given us a standing rule of conduct in matters of common interest where we must be able to separate the genuine from the counterfeit and the true from the false. When an office or rank of responsibility has to be given to a per-son, it becomes necessary to assess the qualification and capability of the incumbent. To do that, the best rule is to go through the record of his past life. If the person concerned is found to be true and trustworthy, the same can be expected from him in the future as well. And if, there is no evidence to prove his honesty and truth in that person's past life, trusting him for the future just because of what he says or claims is not a wise thing to do. In our time, finding the right person for an office of responsibility has become a nightmare. All sorts of errors (of intent, background research and decision making) are being committed and errors are compounded by widespread disorders (in social and governmental institutions). The real reason why all this is happening is the abandonment of this natural principle in favor of what is customary, formal (or straight dishonest).