Thank you very much. If I meet imam in the 3rd Rakat (Ishai prayer-where 3rd and 4th rakats are only Faatihat rakats) and of course complete the 4th rakat with him. Now i have done only 2 rakats. To pray my 3rd and 4th rakats should i read Faatihat only (in the 3rd and 4th rakat respectively) or i should read surat after the Faatihat in the 3rd and also in the 4th rakat. Not reading surat beside faatihat in this case makes all my ishai rakats only "faatihat rakats". Is that OK?
Generally, you can recite the Surah Fatiha (only) in the third and fourth Rek’a (instead of Tasbihat al-Arba’a). (it doesn’t make any difference if you are in Salat-al-Jama’a or not). Hence you shall not recite another Surah … (in accordance with the ruling of Shia)
According to the ruling of Imam Khomeini:
a person who says prayer, he/she can recite Surah al-Fatiha instead of Tasihat al ara’a, but the point is that he ought to recite it slowly (with the low voice) and it is Ehtiat-al-Wajib that he does not recite the Bismillah-al-Rahmane-Rahim loudly (in the 3th and 4th Rek’a)
توضیح المسائل(المحشی للإمام الخمینی) ج1ص 555 مسأله 1005
(Tozih-Al-Masael (Al-Mahshi Lel Imam Khomein) Vol.1, Pg.555 M1005)
So in accordance with the mentioned issue, we can figure out that you ought not to recite another Surah after Surah Al Fatiha …