What should I do? I offered the `Isha' (Night) Prayer in congregation, but I arrived late and missed two Rak`ahs (units of Prayer). When the Imam (the one who leads congregational Prayer) said the Taslim (salutation of peace ending the Prayer), I followed him directly. However, after I had offered the Witr (Prayer with an odd number of units), I remembered that I had only performed two Rak`ahs of the `Isha' Prayer.
It is obligatory on you to repeat the `Isha' Prayer.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.