When the Imaam Forgot to recite Surah Faatihs or another Surah and then did so after Rising from Ruku

Only in Ruku did the Imaam realise that he had not recited Surah Faatiha or another Surah. He then stood up to then be valid after performing Sajdah Sahw? If he needs to repeat the Ruku and a latecomer then joined the Imaam in the second Ruku, will the latecomer be part of the Rakaah just performed?

Answer: It will be necessary to repeat the Ruku in the aforementioned situation Sajdah Sahw should then be performed at the end of the salaah, thereby rendering the salaah valid. The salaah will however be invalid if the Ruku is not repeated. The latecomer's joining the Rakaah before the Ruku will be valid and will not have to repeat the Rakaah. And Allaah knows best what is most correct.

Fatawa Rahimiyyah vol.2