1. Imam praying 3 witr in jamaat, can I make an intention of 4 rakat nafl (or tarawih)and stand up after imam says salaam and complete 1 rakat?
2. Imam praying 3 witr salah, I joined the jamat in the last sajda, but instead of making intention of witr I made intention of 2 rakat nafl, when imam said salam I stood up and completed 2 rakat. Is my salah valid?
Bismillahi Ta’ala
Walaikum Assalam Warahmatullah
It is not permissible to follow behind an imam praying 3 rak’at witr Salah in congregation, and making the intention of 4 rak’at Nafil. One would go contrary to the Imam if he completes 4 rak’at, same as it would be makruh for him to pray 3 rak’at as nafil.
Similarly, one should not join the Imam in last rak’at of his witr, to complete 2 rak’at as nafil for the same reason of going contrary to the Imam.
Wallahu A’lam
And Allah Ta’āla Knows Best
Mufti Faisal al-Mahmudi