Is it valid to combine the Maghrib and Isha prayers as a delayed combination (jam' ta'khir), praying them an hour or more after the Isha prayer [time has begun], by starting with the Maghrib prayer first then the Isha prayer, and what is the fundamental principle regarding combining prayers?

If there is a legitimate excuse that permits combining prayers, then there is no harm in combining the two prayers, either by advancing or delaying them. However, if the combining of prayers is done without an excuse, it is a great sin and a major one. If an excuse for combining prayers exists, then there is no harm in combining them at any part of the time, provided the conditions are met. For combining by delaying, the conditions are the existence of an excuse and the intention to combine during the time of the first prayer. Continuity between the two prayers is not a condition, according to the preponderant opinion. As for combining by advancing, for its validity, the conditions are the existence of an excuse, the intention to combine at the beginning of the first prayer, continuity between the two prayers, and maintaining their order. The basis for the legitimacy of combining prayers comes from the Prophet's hadiths, such as his combining prayers at Arafat and Muzdalifah.