Reappearence of Imam Mahdi (atf) in Quran

Allah states in this verse as a promise which is going to happen surely

"And We have already written in the book [of Psalms] after the [previous] mention that the land [of Paradise] is inherited by My righteous servants."(1) (21:105)

and in other verses, three times in different places He says:

"It is He who has sent His Apostle with the guidance and the religion of truth, that He may make it prevail over all religions"(2) (9:33, 48:28, 61:09)
Under this verse Aytullah Makarim Shirazi says in his commentary Tafsir Nemoone that these verses are reason for great reappearance (of Imam Mahdi aj ) vol 24. P 85

The last parts of the two mentioned verses as an event which is to happen has not accomplished yet and this is the fruit of sending prophets according to the Noble Quran.

Notes:
1. ولقد كتبنا في الزبور من بعد الذكر ان الارض يرثها عبادي الصالحون
2. هو الذي ارسل رسوله بالهدى ودين الحق ليظهره على الدين كله