It is important to understand the meaning and the implications of the second part of the testimony of faith as well. Indeed, sometimes one strays from the Straight Path and from Islam itself because he is not implementing the second part of the declaration of faith properly.
When one testifies that Muhammad is the Messenger of Allah, he is stating his belief that the Prophet Muhammad (peace be upon him) was chosen by Allah to be His Messenger and to convey His Message. Allah specifically chose the Prophet Muhammad (peace be upon him) to be His Messenger.
Allah knows best with whom to place His Message
This implies some characteristics of the Prophet Muhammad (peace be upon him) as obviously Allah, due to His justice, wisdom and mercy, would not choose one who is treacherous or lying to be His Messenger. Allah would not choose anyone for such an important mission whom He knew would not convey the message or who would use the position to his own advantage. If anyone claims that the Prophet (peace be upon him) did not actually convey the entire message or that he distorted it in any way, he is actually saying that Allah did not know who was the correct or best person to be a messenger. This is obvious disbelief.
Second, when one makes the testimony of faith, he is also testifying that the Prophet (peace be upon him) has been sent for all of mankind until the Day of Judgment.
Say [O Muhammad]: O mankind! Verily, I am sent to you all as the Messenger of Allah
It is obligatory upon everyone from the time of the Prophet (peace be upon him) until the Day of Judgment to believe in and follow the Prophet (peace be upon him). This also implies that the Prophet’s teachings and his Sunnah are valid and obligatory upon all of mankind until the Day of Judgment.
Some people seem to try to resist the idea that they have to follow the Prophet (peace be upon him). When they do so, they must realize that they are going against what they have testified to. They have testified that the Prophet’s message, which includes both the Quran and his inspired Sunnah, is for all of mankind— including each and everyone alive today.
when one makes the declaration of faith, he is testifying that he believes with certainty that the Prophet Muhammad (peace be upon him) conveyed the message— he conveyed it correctly, he conveyed all of it, and he conveyed it clearly.
The Messenger’s duty is only to convey (the message) in a clear way
The Prophet (peace be upon him) himself said
I left you on a bright path whose night and day are alike. No one strays from it after me except he is destroyed
Recorded by Ahmad and al-Baihaqi. According to al-Albani, it is sahih. See Muhammad Nasir al-Din al-Albani, Sahih al-Jami al-Sagheer (Beirut: al-Maktab al-Islami, 1986), vol. 2, p. 805.
The Prophet (peace be upon him) conveyed all of the guidance and revelation that he received from Allah. He conveyed and explained it in a clear manner. Therefore, one is also testifying that the Prophet (peace be upon him) conveyed all the aspects of the religion– its fundamental as well as its secondary aspects. There is no part of the religion that one needs for his guidance that was not conveyed to mankind or that Allah or the Prophet (peace be upon him) may have possibly forgotten.
Therefore, when this complete and clear guidance from the Prophet (peace be upon him) is present, there is no need for any Muslim to turn to other sources for guidance. There is no need for one to turn to the books of the Jews or Christians. Indeed, the Prophet (peace be upon him) told Umar, when he saw him reading the Torah, that if the Prophet Moses were alive at his time, he would also have to follow the Prophet Muhammad (peace be upon him). There is no need for any Muslim to turn to the Greek philosophers, for example, to learn about theology.
In fact, there is no need for Muslims to turn the religious or spiritual teachings of any non-Muslims to get guidance. All that is needed is to be found in the Quran and Sunnah. This is part of what the Muslim is testifying to. The Muslim bears witness that the Prophet (peace be upon him) conveyed the entire message.
When one declares, “Muhammad is the Messenger of Allah,” one is also declaring that he is the final prophet sent by Allah.
Muhammad is not the father of any man among you, but he is the Messenger of Allah and the Last of the Prophets
There is to be no prophet who is going to come after the time of the Prophet Muhammad (peace be upon him). No new prophet and no new scripture will come that will abrogate what the Prophet Muhammad (peace be upon him) brought. Furthermore, if anyone after the time of the Prophet Muhammad (peace be upon him) claims to be a prophet, it is known automatically that such a person is a liar and a deceiver. He must be opposed and it should be declared to all that his claim to prophethood is false. To accept anyone as a prophet after the Prophet Muhammad (peace be upon him) is to falsify one’s declaration of the testimony of faith.
It must also be realized that when one makes the testimony of faith, this not only implies that he believes in certain things but it also implies that he accepts certain responsibilities that stem from it. For example, when he says that there is none worthy of worship except Allah, for that testimony to be true, it means that he is now taking on the responsibility of worshipping no one other than Allah.
Similarly, when one says, “I testify that Muhammad is the Messenger of Allah,” he is taking on certain responsibilities with respect to the Prophet Muhammad (peace be upon him). When he is lacking in any of these responsibilities, then he is lacking in his complete fulfillment of his testimony of faith. It can even get to the point that he negates his testimony completely by refusing to fulfill his responsibility to the Prophet Muhammad (peace be upon him).
One of these obligations toward the Prophet (peace be upon him) is to love him. This does not just imply any form of love but complete faith requires that one loves the Prophet (peace be upon him) more than anyone or anything else of this world.
Say: If your fathers, your sons, your brothers, your wives, your kindred, the wealth that you have gained, the commerce in which you fear a decline, and the dwellings in which you delight are dearer to you than Allah and His Messenger, and striving hard and fighting in His cause, then wait until Allah brings about His Decision (torment). And Allah guides not the people who are disobedient
Second, when one makes the testimony of faith, this means that he is accepting the Prophet Muhammad (peace be upon him) as his example of how to live and behave in a way that is correct and pleasing to All
Indeed in the Messenger of Allah you have an excellent example to follow for him who hopes in (a good meeting with) Allah and the Last Day and remembers Allah much
Say (O Muhammad): If you love Allah, then follow me and Allah will love you and forgive you your sins
It is very strange that some people actually state the testimony of faith and declare that Muhammad is the Messenger and Prophet of Allah yet at the same time they do not consider him an example of the way of life that a believer should follow. Not only do they not take him as an example for themselves, they actually oppose others who do take the Prophet (peace be upon him) as their example. This is nothing but a clear sign that such a person does not have a clear understanding of the meaning and implications of the testimony of faith that he made.
The Prophet (peace be upon him) has said
I swear by Allah that I am the most fearful of Allah and most conscious of Him than all of you. But I also [as part of my Sunnah] fast and break my fast, pray and sleep [at night] and I marry women. Whoever turns away from my Sunnah is not from me [that is, is not one of my true followers]
 In this hadith, the Prophet (peace be upon him) explained that he is the most fearful of Allah and God-conscious. Therefore, there is no excuse for anyone not to follow his example and guidance. But he also stated that the one who turns away from his practice and example is not from him. One cannot truthfully claim to believe in and accept the Prophet Muhammad (peace be upon him) and, at the same time, refuse to accept his life as the example that one must strive to emulate.
- It is true that the Prophet Jesus (peace be upon him) will return. However, when he returns, he will not do so in the role of a prophet or messenger. He will be only a follower of the Prophet Muhammad (peace be upon him) and his Law.