The Book of marriage From The Explanation of Bulugh Al-Maraam Part 3 By Shaykh Muhammad Bin Salih Al-Uthaymin

‘Ali Ibn Abū Ṭālib is the cousin of the Messenger (ﷺ), and Fāṭimah is the daughter of the Messenger (ﷺ), the most prestigious lady in Paradise (رضي الله عنها) as stated by the Prophet (ﷺ). Additionally, the Prophet (ﷺ) said about ‘Ali (رضي الله عنه):

“You are in the same position with relation to me as Aaron (Hārūn) was concerning Moses but with (this explicit difference) that there is no prophet after me.”

He said this when he delegated him the responsibility of [Madīnah] when Muslims were away in the Tabūk conquest. So, he said: O Messenger of Allāh! You leave me behind with women and children? To warm his heart, the Prophet (ﷺ) said the above narration. It is also because Aaron (Hārūn) took Mūsā’s place among his people, as he said:

“Replace me among my people.” [Sūrah ’Al-A‘rāf (7):142]

The previous Āyat explains the following statement: “You are in the same position with relation to me as Aaron (Hārūn) was concerning Mūsā.”

However, as the Prophet (ﷺ) feared that anyone would misuse this word and claim that ‘Ali is a Prophet like Hārūn, he said:

“but with (this explicit difference) that there is no prophet after me.” This statement highlights the immense protection the Prophet (ﷺ) dedicated to the prestige of the Message [of Islām]. Also, he is concerned about the importance of Tawhid (Islāmic Monotheism). Certainly, according to the Qur’ān and the Sunnah, it is well-known that he is the last of the Prophets, and there is no Prophet after him.