The Book of Prayer - Travellers
6/5. Chapter:
It is permissible to combine two prayers when traveling
Sahih Muslim
وَحَدَّثَنِي حَرْمَلَةُ بْنُ يَحْيَى، أَخْبَرَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي يُونُسُ، عَنِ ابْنِ شِهَابٍ، قَالَ أَخْبَرَنِي سَالِمُ بْنُ عَبْدِ اللَّهِ، أَنَّ أَبَاهُ، قَالَ رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم إِذَا أَعْجَلَهُ السَّيْرُ فِي السَّفَرِ يُؤَخِّرُ صَلاَةَ الْمَغْرِبِ حَتَّى يَجْمَعَ بَيْنَهَا وَبَيْنَ صَلاَةِ الْعِشَاءِ .
Salim b. 'Abdullah reported that his father had said: I saw the Messenger of Allah (ﷺ) delaying the sunset prayer till he would combine it with the 'Isha' when he hastened to set out on a journey.
Reference : Sahih Muslim 703dIn-book reference : Book 6, Hadith 55USC-MSA web (English) reference : Book 4, Hadith 1511