We have said that despite the differences in details all Prophets have delivered the same message and belonged to the same ideological school. The principles and teachings of this school were explained to human society gradually in proportion to its development till the humanity reached the stage when the entire teachings in a comprehensive form were presented. At this point Prophethood came to an end. The Holy Prophet, Muhammad bin Abdullah (Peace be on him and his progeny) was the person through whom the complete ideology was conveyed, and the Holy Qur'an was the last celestial Book. The Holy Qur'an itself says: "In truth and justice has been perfected the word of your Lord. None can change His words." (Surah al-An'am, 6:115)

Now let us see why in the past the Prophethood was renewed from time to time and so many Prophets were raised in succession, though most of them were not given a new and independent code of law and were sent to promulgate then existing code? Why did this procedure come to an end with the last Prophet since whose time no Prophet, neither a law-giving one nor a preaching one has come, nor will ever come? Here we touch upon the reasons briefly.
Reasons of the Renewal of Prophethood
Though Prophethood is one continuous process and the Divine message, as the religion is not more than one reality, the reasons of the appearance of so many law-giving and preaching Prophets in succession and the termination of Prophethood after the advent of the last Prophet are as under:
Firstly the ancient man because of his intellectual immaturity was unable to preserve his celestial Book. Usually the Divine Books were either altered and corrupted or were lost totally. Therefore it was necessary that the message should be renewed from time to time. The revelation of the Holy Qur'an corresponded with a period when humanity had passed the period of its childhood and had become able to preserve its intellectual heritage. That is why there could be no alteration in the last Divine and Holy Book. The Muslims committed to memory and recorded in writing every verse of it as it was revealed, and did away with every possibility of addition, omission or alteration in it. Thus one of the reasons of the renewal of Prophethood disappeared.
Secondly, humanity being immature, it was not previously competent enough to have a comprehensive plan for its guidance, and hence it was necessary that it should be guided by the Prophets piecemeal and step by step.
Anyhow, by the period of the final Prophethood humanity had developed to the extent that it was able to have a comprehensive plan of conduct and it was no longer necessary that it should receive guidance stage by stage. Besides the extinction of the old celestial Books and the alteration in them, another reason for the continual renewal of Prophethood was that man in olden days was not able to receive a comprehensive plan. When his ability sufficiently developed, a comprehensive scheme was put at his disposal and this reason of the renewal of Prophethood also disappeared. Now the Muslim scholars who were specialists in this field, can guide the Muslims in the light of this scheme and can frame the rules and procedures for them to suit every occasion.
Thirdly, the overwhelming majority of the Prophets consisted of the preaching and not the law-giving Prophets. The number of the law-giving Prophets did not exceed the number of the fingers of one hand. The task of the preaching Prophets was to propagate, interpret and promulgate the religious law prevailing during their time. Now the religious scholars of the age of the finality of Prophethood, which is the age of knowledge, are capable of applying the general principles of Islam to the requirements of the time and place and deducing the rules of religious laws. This process is called ijtihad. The outstanding Muslim divines in this way perform many duties of the preaching Prophets and some of those even of the law-giving Prophet without being the law-givers themselves. They guide the Muslim Ummah. Thus, though the need of religion still exists and is expected to be ever increasing with the further cultural development of humanity, the need of the new Prophets and the new revealed Books has ceased to exist. And hence Prophethood has come to an end with the final Prophet. It is clear from what has been mentioned that intellectual and social maturity of mankind has played a big role in the finality of Prophethood in several ways:
(i) It has enabled man to keep his celestial Book unaltered.
(ii) It has enabled him to receive his evolutionary programme all at once and not by stages.
(iii) It has enabled him to undertake the task of preaching and propagating religion, to set up religious institutions, to exhort people to do what is good and to restrain them from what is evil. Thus there is no longer any need of preaching Prophets who used to preach and propagate the teachings of the law-giving Prophets. This need is now being adequately fulfilled by the religious scholars and Divines.
(iv) From the viewpoint of mental development man has now reached a stage that in pursuance of his ijtihad he can interpret the revealed words and can apply the relevant principles to all the changing circumstances. This task is also being performed by the religious scholars.
It is evident that the finality of Prophethood does not mean that man is no longer in need of Divine teachings received through revelation. Prophethood has not come to an end because as the result of his mental development man is now able to dispense with religion.