Salat started later

Question

I was there in mosque when Iqamat was being given. But intentionally I stared after sometime when salat was started as I have make my dress wel prepared for salat. Then I joined. It was still salat going on in 1st rakaat and Ruku was not made still started reciting sana then told Aa'udhubillah then Bismillahi rrahmaaani rrahiiim as soon as I tell it the imam goes for ruku. So I can't start Sura Fatiha. Will my salat be valid as I go for ruku without reciting at least one verse from the holy Al Qur'an though reciting at least one verse from Al Qur'an is farz?
Please answer my question by mentioning ayats of Al Qur'an and sayings of Prophet (sm) as I don't know whether to repeat the Salat or not

Answer 1

First you shouldn't waste time once the call for prayer has been made. And if you had the time to recite al-Fatiha before the Imam stands up from ruku' you should do so!

Second if your prayer is invalid so how about a person who reaches the lines once the Imam moved to ruku'?
Of course al-fatiha is considered as fard but not for all madhabs. On the other hand to recite al-fatiha fully you must join the prayer while the Imam is standing not right before he moves to ruku'. Yes we have the hadith saying:

"Whoever does not recite Al-Fatiha in his prayer, his prayer is invalid." (See for example in sahih al-Bukhari)

But this hadith doesn't explicitly say in each rak'a! And of course hadiths such as this from sunan abi Dawod support the view of reciting it, even if hanafi scholars say it is not necessary for a follower to recite behind the Imam.

But we on the other hand have a hadith which clearly say if we join a congregation and could perform at least one ruku' in a complete manner the rak'a counts fully so we are not asked to add this rak'a to what we may have missed before (including the recitation of al-fatiha).
See for example in sahih al-Bukhari and sahih Muslim, while this version from sunan abi Dawod is more explicitly explaining the matter:

when you come to pray while we are prostrating ourselves, you must prostrate yourselves, and do not reckon it anything (rak’ah) and who finds a rak'ah, he in fact finds the prayer.

Please note that the translation of this hadith is not correct so may quote is a corrected version of the linked hadith!

From this -technical- perspective of course your prayer is valid but you missed to gain thawab (rewards) for reciting al-fatiha due to a possibly waste of time. As you should have been in the line of the congregation once the Imam starts the prayer as you apparently where at the mosque!

... as I don't know whether to repeat the Salat or not

of course you are free to repeat it, note that even a minority of scholars consider not reading al-fatiha a reason for repeating a prayer or adding a raka'a even if the above evidences are stronger and show that it is not necessary, if one missed the qiyam!

Read also this fatwa in English.