Muhammad, the Last Prophet
All Muslims of the world, no matter what their sects are, hold in common that the Holy Prophet of Islam was the last prophet, and in fact, Muslims believe in divine prophecy having ended with him, just as they believe in the Unity of God.
Islam is always fresh, wonderful, and comprehensive, and the more extensive is one's insight, the more one comprehends the comprehensiveness of Islam. As a matter of fact, there is no end to Islam's wonders and,miracles.
Now let us survey the truth of this belief. First we will explain the most effective reasons for a faith being eternal, and then we will consider Islam.
The most important factor causing a faith to persist and enjoy perpetuity is its being consistent with and based on human nature. A religion of which the instructions are in accordance with natural and innate human characteristics will continue to prevail forever, will never suffer annihilation as a result of the passing of time, nor will such a faith become out of date and useless.
Instructions and precepts that are not restricted to a certain place or period of time are compatible with any kind of progress and will stay as valid and powerful as they have always been no matter how many changes take place in the material aspects of human life and how much advance is made in technology and natural sciences.
On the contrary, instructions and rules that are limited to a particular period or a special group fail to fulfill all aspects of human needs at all times and under all circumstances. For example, if a rule is made that commands people are only allowed to use natural vehicles such as horses and camels for traveling and transportation, such a rule will obviously be discarded and outdated because new necessities make people utilize new means and equipment. One of the reasons why past faiths are not durable is that they have been meant for a certain group or a special period of time.
Comprehensiveness: An eternal faith must be all-embracing, comprehensive, and able to meet all human needs and wants. It is an already experienced fact that man's thirsty, stormy soul does not find peace and satisfaction with a series of empty ceremonies but is in great need of comprehensive precepts and rules that are capable of guiding him all through his life, of providing solutions to his various problems both in personal and social life, and of satisfying his spiritual demands and wants.
Giving guidance in deadlocks: There are certain occasions in human life when either due to the conflict of general rules or due to an unexpected emergency, man finds himself in a deadlock and starts wondering what to do and how to proceed.
Thus an eternal faith must, in addition to overall rules and instructions, provide man with other sets of rules and guidelines that explain the solutions to exceptional problems and emergency situations that general rules are incapable of handling.
And it is such a comprehensive faith that is in accord with all times and all conditions of life and can benefit all. In fact, it is only a perfect faith that serves the supreme purpose of leading human beings onto God's path. The foregoing factors are the most significant causes of the duration and perpetuity of a faith all of which are in Islam. Now let us find some explanations for these factors.
Islam: The Immortal Faith
It is a reality that, in the legislative system of Islam, human nature, which is the same at all times and in all places, has been taken into consideration and positive answers have been given to natural human wants and needs. A careful study of Islamic precepts and programs reveals the fact that they have been so designed as to regulate all human instincts.
For example, for the proper satisfaction of human sexual instincts, various simple plans and rules have been offered that properly satisfy and regulate this natural instinct at the same time that they prevent unrestrained sexual relations, so human societies may be immune from the corruption and decline that sexual freedom causes.
The fundamental rules anti laws in Islam are meant not just for a particular time or a particular place needing modification and change as conditions change, they are compatible with all environments and all times and are capable of providing human beings with all the guidelines they need to live happily and prosperously and to find eternal salvation as well.
In the Islamic programs and teachings concerning jihad, for instance, no emphasis is placed upon weaponry and tactics of the time of the Prophet, such as fighting with swords. Rather, Islam has given this general command concerning jihad: Strengthen your fighting abilities, mobilize your forces, and acquire good arms and ammunition so you will be able to defend your vital rights against your enemies and overcome them. This is a general all-embracing rule that is in accordance with all conditions of life and all sorts of progress made in technology.
And thus this comprehensive rule can invariably give guidance on the questions concerning war in Islam, and the same is the case with other Islamic rules and instructions.
To the deadlocks and emergencies that occur in human life, either individual or social, the faith of Islam has offered laws such as 'the law of emergency', 'the law of not guilty', 'the law of no loss',  and the like, which present suitable solutions to all problems, however complicated they might be. Moreover, the Imams, the successors of the Holy Prophet of Islam, and religious leaders whom Muslims follow can offer decisive solutions to social deadlocks and problems.
The programs and rules designed by Islam are far more extensive and elaborate than those presented by other schools of thought. In Islam, all legal, economic, military, moral, and other issues and points have been presented and surveyed in the most elaborate and perfect manner. The Islamic theologians have so far compiled thousands of books on the fore-going subject for which the sources are the Holy Qur'an, the sayings of the Holy Prophet of Islam, and the teachings of the offspring of Prophet.
Thus, taking into consideration these facts and proven realities, any knowledgeable person will admit that Islam is a perfect faith, capable of fulfilling human needs and of presenting solutions to all problems, and so there is no need for any other faith or any new school of thought.
The End Of Prophecy With The Prophet
The comprehensiveness of the rules and precepts of Islam and the end of prophecy with the Holy Prophet of Islam have been clearly expressed in the Qur'an: 'And the word of your Lord has been accomplished truly. and justly; there is none who can change His words, and He is the Hearing, the Knowing' (6:115).
'Muhammad is not the father of any of your men, but he is the Messenger of God and the Last of all Prophets, and God is cognizant of all things' (33:40).
In the Arabic language, wherever the word 'khatam' is attached to a word, it conveys the meaning of 'the last' and in this verse it refers to 'the last of the prophets'. Nabi means any type of divine messenger. 
Obviously, the word messenger can be applied to all prophets so by saying that Muhammad is the last of all prophets, God means that he is the last of all messengers and that after him there will come no prophet, nor any messenger from God, nor any person with a new holy book.
'Surely this Qur'an guides to that which is most upright and gives the good news to the believers who do good that they shall have a great reward (17:9).
Therefore, human beings have no need for any other prophet, any other rules and regulations, or any other school of thought because all they need is to be found in the Qur'an.
There are so many documents and testimonies to the fact that the Prophet was the last of all prophets that in Islam this reality is considered one of the clearest points.
Now your attention is drawl to some narrations:
The Prophet has himself said, 'You must know that there will come no Prophet after me and no faith after my faith of Islam...'. 
Imam Baqir (peace be upon him) has said, 'God has ended Holy Books with your Book, the Qur'an, and prophets with your Prophet...'. 
Hazrat 'Ali (peace be upon him) has said, 'God assigned Muhammad, peace and the mercy of God be upon him and his descendants, to be a prophet after all other prophets and has ended revelation with him'. 
The Prophet said to Hazrat 'Ali, 'Your relation to me is like that of Aaron to Moses, peace be upon him, with the difference that there will come no prophet after me'." 
Imam Riza (peace be upon him) has said, 'The faith of Muhammad (peace and the mercy of God be upon him and his descendants) will not be abolished until the Day of Resurrection, and no prophet will come after him until that day'. 
These and many other traditions and narrations are perpetual proclamations of the Prophet as the last of all prophets and Islam as the only comprehensive faith.
The splendour of the purport of this faith as well as its profound precepts and comprehensive rules ensure its perpetuity till the Day of Judgment.
Now that God has endowed us with such a matchless magnificent faith, surely it is our duty to communicate it to all other people so all will benefit from this holy faith.
. The law of emergency is applied in emergency situations. The law of non-guilt is applied in cases of severe trouble. The law of no loss is applied when a loss may occur. The conditions and qualifications of these laws have been explained in detail in the books on theology wind jurisprudence.
. Jami' ul-Javami', p.275; Tafsir al-Mizan, Vol. 2, p.144; Tafsir ul-Kashif, Vol. 3, p.164; Tafsir ul-Biyadwi, p.477; al-Bayan, Vol. 7, p.91; Ruh ul-Ma'ani, Vol. 22, p.32.
. Mustadrak, Vol. 2, p.262.
. Usul ul-Kafi, Vol. 1, p.177.
. Najh ul-Balaghah, Fiyd ul-Islam, sermonn 133, p.403.
. Kamil, Vol. 2, p. 278.
. Uyun akhbar ul-Reza, Vol. 2, p.80.
Taken From: A Glance at the Life of the Holy Prophet of Islam , by Dar Rah Haqq's Board of Writers , Translated by: N. Tawheedi