Is it permissible to combine the Maghrib and Isha prayers due to rain for someone who missed the Maghrib prayer with the Imam but caught the beginning of the Isha prayer?

It is permissible to combine the Maghrib and Isha prayers due to rain.

If the Maghrib prayer is missed, scholars differ regarding the validity of praying Maghrib behind an imam who is praying Isha. Those who permit it state that the worshipper can intend to pray Maghrib, then sit and make the taslim after three rak'ahs, and then pray Isha with the imam.

If one has already prayed Maghrib without the intention of combining, and then finds an imam praying Isha in combination with Maghrib, it is permissible for him to join them in the Isha prayer to attain the virtue of congregational prayer. Some scholars are of the opinion that the intention of combining is not required in this case.