A man who was travelling performed Maghrib then another group came and he wanted to join them, is it permissible for him to join their jamaa and pray with them Maghrib with the intention of praying Isha whereby he remains seated after the first tashahud and wait till he does taslim with the Imam at the same time, or he does taslim when the Imam is standing up for 3rd rak’ah.
صلاة المغرب خلف من يصلي العشاء