Imam Mahdi and the Hour Prophecy in the Quran

Allah Almighty mentions the Hour (al-Sa'a) several times in the chapters of the Quran, and the verb "to rise" (yaqum) is normally used for people, not for time. 

We do not say "the Hour has risen," but rather "the Hour has come," or "the time has come," or "it's about time," or "such-and-such a day has come." This suggests that the prophecy of the Hour (al-Sa'a) is likely about the Mahdi and his rising at the end of time. Among the titles of the Mahdi is "al-Qa'im" (the Riser), and he is mentioned with this title in the Book of Isaiah. Likewise, there is a hadith attributed to the Imams of Ahl al-Bayt that explains the meaning of the Hour (al-Sa'a) in the Quran.

The hadith reads as follows:

On the authority of Mufaddal bin Omar, he said: "I said to Abu Abdullah, peace be upon him, about Allah Almighty's saying, 'Nay, they deny the Hour, and We have prepared for those who deny the Hour a blazing Fire.' He said to me: 'Allah created the year with twelve months, made the night twelve hours, and made the day twelve hours. From us there are twelve inspired ones, and the Commander of the Faithful, peace be upon him, was one of those hours.'"

On the authority of Abu al-Sa'ib, he said: "Abu Abdullah Ja'far bin Muhammad, peace be upon him, said: 'The night is twelve hours, the day is twelve hours, the months are twelve months, the Imams are twelve Imams, the leaders are twelve leaders, and Imam Ali is one hour out of the twelve hours, and this is the saying of Allah Almighty: "And We have prepared for those who deny the Hour a blazing Fire."

In addition to the year having twelve months and the day and night each having twelve hours, Allah Almighty willed that both the Arabs and the Hebrews be divided into twelve tribes. This further clarifies the meaning of the Hour in the Quran and in the hadiths mentioned above.