“’Haa, Meem, Ayn, Seen, Qaaf”
Imam Baqir (as) said, “’Haa, Meem, Ayn, Seen, Qaaf” refers to the number of years of the Qaem (as) and Qaaf is a mountain made of green emerald that surrounds the world. The green colour that appears in the sky emanates from that mountain. And the knowledge of everything is within “Ayn, Seen, Qaaf” (Tafseer Al Qummi volume 2 page 267)
Imam Baqir (as) said, “Haa, Meem” stands for Hatm (inevitable).
“Ayn” stands for Adhaab (torment).
“Seen” stands for Sinoon (years), just like the years of Yusuf (as)#.
“Qaaf” stands for Qadhf (intense strikes), for the collapse (of the earth), and for the deformation (of the people) – all of which will occur at the end of time to Sufyani and his thirty thousand companions from among the Bani Kalb. This will take place after the rising of the Qaem (as) from Makkah, and he (as) is the Mahdi of this nation. (Taweel Al Ayat Al Zahirah page 528)
#Note: Hazrat Yusuf (as) was also in occultation and his occultation is given as an example for the occultation of Imam Mahdi (as) in which people could see him but not recognise him as being Prophet Yusuf (as).