There is no doubt that the prophet of Islam is the last prophet of Allah, and that after him legislative revelations were no longer sent down. As Imam Ali stated while performing Ghusl on the prophet’s body: “O' Messenger of Allah! With your death something has been taken away from us what would not have been taken away at the death of any other individual, and that is prophethood and heavenly revelations.”[1] Therefore, this issue (Khatamiyyah) is one of the main Islamic teachings.

When refuting the argument mentioned in the question, we must shed light on a few points:

1- One of the causes of the arising of such a question is not differentiating between prophethood and Imamate. In the science of Kalam, or Islamic theology, the term Nabiyy (prophet) refers to one who not only possesses features such as knowledge, infallibility, and having to be obeyed, but also actually claims prophethood and receiving revelation from Allah, and if need calls, has the power to present a miracle. Therefore, in prophethood, reception of revelation and presenting miracles are central factors. These are exclusively for the prophets, and imams have never had such claims and their Shias have never overrated their leaders to such extent for their belief to contradict Khatamiyyah and lead to exaggeration.

2- There is no discrepancy between Khatamiyyah and others being granted knowledge and thier knowledge being binding on other people during the period of Khatamiyyah. A group of people (other than the prophets) are mentioned in the Quran as “those who have been given knowledge”; that knowledge has been granted to them without any effort on their part for its attainment, “هو آیات بینات فی صدور الذین اوتوا العلم”[2]. Even though those who possess this knowledge are gifted by Allah, they are not prophets and solely seeing the angels or having knowledge of the Gheib (unseen) does not lead to prophethood. Allah’s angel appeared before Lady Maryam and granted Prophet Isa to her, but that didn’t make here a prophet. Therefore, the knowledge that the Imams possess is of the kind mentioned above and, as a result, the Imams can have such knowledge and not be prophets at the same time.

It must be mentioned that the sources from which the Imams gain knowledge are many, most notably, Ilham (inspirations) which is a non legislative type of revelation and can be received by individuals that are not prophets.[3]  Another source from which the Imams gain knowledge is inheriting it from the prophet. It is transmitted by Shia and Sunni narrators that Imam Ali stated: “علمنی رسول الله الف باب، کل باب یفتح الف باب”[4] “The prophet taught me a thousand doors (fields) of knowledge and every door would open up to another thousand doors (fields) of knowledge.” This knowledge was only completely transmitted to Ali Bin Abi Talib and made him the “باب علم نبی” “The door to the prophet’s knowledge”, and it was of the kind that is granted and not accumulated, that Allah grants to whomever he wills. This is why this knowledge is binding on those who don’t possess it and this also explains why the prophet has placed bearers of such knowledge next to the Quran: “انی تارک فیکم الثقلین، کتاب الله و عترتی ...”[5] Therefore, Khatamiyyah does not mean that after the seal of prophethood, the words of the infallible leaders are not binding on the people, in fact, when observing Khatamiyyah precisely, one can conclude that the words of the Imams can be binding if they do not have to do with what is exclusively allocated to the prophet, meaning that if what they are saying is other than what only the prophet has the right of speaking of, then it is mandatory for all to follow. Taking what was said into consideration, claiming infallibility, possession of divine knowledge and having a connection with the unseen through divine inspiration and receiving non-legislative revelation (e.g., revelation on Islamic rulings) are not always accompanied with prophethood and none of the Shia scholars has ever claimed such a thing.

3- The one who poses this theory that suggests a contradiction between Imamate and Khatamiyyah tries to lower the status of the Imams to that of normal people through Khatamiyyah and through the fact that the prophet of Islam was the seal of all prophets. However, this individual must accept the prophet himself as the Hujjah of Allah and must adhere to his words without question.[6] In other words, he must accept the implications of his claim, meaning that he must accept the ahadith that are narrated from the prophet in regard to Imam Ali’s status and greatness. Upon the slightest scrutiny of the prophet’s words, one can conclude that according to the command of Allah, both the prophet and Imam Ali enjoyed an authority that leads to their words being Hujjah and binding on others and having Wilayah and authority over them.

The prophet of Islam has granted Imam Ali Imamate and Wilayah of all religious issues and matters and has considered him as his successor in these affairs through the hadith of Manzelah[7] and other ahadith as well as many Quranic verses, and this inevitably leads to the Imam’s words and conduct being Hujjah and binding on other Muslims.

Below we will mention a few of these verses and ahadith:

1- In the Quran, Allah has mentioned that the believers’ guardian is only Allah, His Apostle, and the faithful who give the Zakat while bowing down: “انما ولیکم الله و رسوله و الذین آمنوا الذین یقیمون الصلاة و یؤتون الزکاة و هم راکعون”[8] The prophet has explained in many ahadith that the sole example of the term “یؤتون الزکاة و هم راکعون” is Imam Ali.[9]

2- A verse from the Quran commands believers to obey Allah, his prophet and “those vested with authority among you”: “اطیعوا الله و اطیعوا الرسول و اولی ‌الامر منکم”[10] The prophet has expounded in many ahadith that “اولی ‌الامر” refers to Imam Ali.[11] The prophet also commands believers to obey Imam Ali in other ahadith. For example he stated: “و ان امامکم علی بن ابی‌طالب، فناصحوه و صدقوه؛ فان جبرئیل اخبرنی بذلک”[12] There many ahadith in this regard that are beyond the scope of this article.