ANSWER:

If this is in loud prayers, the prayer is valid even if you didn’t read it as the recitation of the imam is sufficient for those who are praying behind him. 

But if it is a silent rakah, not reciting the fatiha voids the rakah as it is a pillar and you must offer another rakah for that if you are certain that you didn’t recite it. 

I know that salaah without surah Fatiha is invalid, sometimes i forget to read after the imam reads and sometimes I’m doubting whether I read or not. Shall I repeat the Salaah or pray two sajda after salaam. Please advise i get this frequently.

Prayer | August 21, 2020 1:44 am
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I am going to my relatives who live around 100 miles way and I am staying there for 2 to 3 days so I will have to shorten my prayers unless I pray with the imam,my question is based on the fact I heard you can’t pray sunnah or nafl on traval,does this also include for the night prayer or am I able to pray that as he night prayer is a nafl?
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Do you have to do wudu before walking to the masjid to get the reward and expiation of sins with each step or would you still get that even if you only make wudu when you arrive at the masjid