Ruling on joining the imam in the tarawih prayer with the intention of 'Isha'

Question:
The brother A. A. A. from al-Madinah al-Munawwarah says in his question: We observe in some mosques that those who arrive after the completion of the 'Isha' prayer and the beginning of the tarawih prayer establish a second prayer, and by doing so, they disturb those who are praying tarawih. Is it better for them to establish the prayer in congregation, or to join the imam in the tarawih prayer with the intention of 'Isha'? Does the ruling differ if the one entering is an individual or a group? Please issue a ruling for us, may Allah prolong your life in His obedience.

Answer:
If the ones entering are two or more, it is better for them to establish the prayer on their own, meaning the 'Isha' prayer, and then join the people in the tarawih. And if they join the imam with the intention of 'Isha', then when the imam concludes the prayer, each one stands and completes it for himself, and there is no harm in that; because it is established from Mu'adh (may Allah be pleased with him) that he used to pray the 'Isha' prayer with the Prophet (peace and blessings be upon him) as its obligatory portion, then he would return to his people and pray that prayer with them, so it was a voluntary prayer for him and an obligatory prayer for them. As for if the one entering is a single person, it is better for him to join the imam with the intention of 'Isha' so that he obtains the virtue of the congregation. When the imam concludes the prayer from the two rak'ahs, he stands and completes the 'Isha' prayer for himself. May Allah guide everyone to understanding in the religion.