Is it permissible to combine the Maghrib and Isha prayers, or to offer the Isha prayer earlier during summer due to its lateness and proximity to Fajr?

It is obligatory to perform prayers at their prescribed times, but it is permissible to combine them notionally (al-jam' al-suri) when there is a need. This involves delaying Dhuhr until the end of its time and performing 'Asr at the beginning of its time, and similarly for Maghrib with 'Isha'. It is not permissible to combine Maghrib and 'Isha' on a continuous basis unless there is an excuse. If the time for 'Isha' disappears, its time should be estimated after Maghrib based on the timing of the nearest country where the signs of the time are apparent. This is supported by the Hadith (definition) concerning the Dajjal: "Estimate for it its measure."