All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
It is not permissible to combine the Maghrib and 'Ishaa’ prayers just because the time is late, rather it is an obligation to perform each prayer at its prescribed fixed time. If the time between Maghrib and 'Ishaa’ is long and a person needs to rest before going to work and the like, then he may sleep and set an alarm clock in order to wake up for the 'Ishaa’ prayer.
For more benefit, please refer to Fatwa 88062.