The Messenger of Allah (saas) said: "Hazrat Mahdi (as) is one of the Ahl al-Bayt. ALLAH WILL PURIFY [MATURE] HIM IN ONE NIGHT."(Al-Muttaqi al-Hindi, Al-Burhan fi Alamat al-Mahdi Akhir az-Zaman, p. 19)
He is called the Mahdi BECAUSE HE HAS A SECRET POWER THAT CANNOT BE KNOWN BY ANYONE. (Al-Muttaqi al-Hindi, Al-Burhan fi Alamat al-Mahdi Akhir az-Zaman, p. 19)
One account speaks of the blessed Mahdi (as) as “MATURING IN ONE NIGHT,” while another reveals that “he possesses a special knowledge.” These statements suggest that Hazrat Mahdi (as) “will attain extraordinary knowledge” “in that night.” It appears Hazrat Mahdi (as) will further mature by way of that extraordinary knowledge he possesses and that his faith will be perfected.
This information imparted in the hadith indicate that in one respect the Hazrat Mahdi (as) will have ilm al-Ladun, while in another he will possess special knowledge not known to anyone else.