Due to the importance of this concept, there are thousands of narrations from Prophet Muhammad (PBUH) and each of the Shia Imams about Imam Mahdi, his occultation, and his reappearance. The belief in Imam Mahdi has been an essential part of Shia theology since the time of the Prophet. There are many historical records and narrations to validate his Imamat and occultation. The Shia scholars had spread the narrations about Imam Mahdi even before his birth. Some of them also authored specific books about Imam Mahdi and his occultation. The names of about 30 such books, written before the birth of Imam Mahdi, are available in history. For example, Fazl ibn Shazan, a great scholar in Khorasan who passed away during the Imamat of Imam Askari, wrote multiple books about Imam Mahdi and his occultation.

The belief in the Mahdi is not just specific to the Shia Muslims; all the Muslims believe in the Mahdi, who is from the Prophet’s descendants. There are various narrations from Prophet Muhammad (PBUH) about the Mahdi, which have been recorded in top narration books of the Sunni sect of Islam. The Sunni scholars have also authored various books about the Mahdi throughout history. Many non-Shia Muslims have tried to misuse the concept of the Mahdi to their own benefit throughout history. They would not have tried to misuse this concept if it was not important and well-known to the Muslims. For example, Mansur, the second Abbasid Caliph, named his son Muhammad and called him by the title of Mahdi. Mahdi then replaced his father as the third Abbasid Caliph. Other examples of famous people who falsely claimed to be the Mahdi in our contemporary time are Muhammad Ahmad in Sudan, Ali Muhammad Bab in Iran, Mirza Ghulam Ahmad in India, and Muhammad ibn Abdullah al-Qahtani in Saudi Arabia.