The Book of Prayer - Travellers
6/5. Chapter:
It is permissible to combine two prayers when traveling
Sahih Muslim
حَدَّثَنَا يَحْيَى بْنُ يَحْيَى، قَالَ قَرَأْتُ عَلَى مَالِكٍ عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، قَالَ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا عَجِلَ بِهِ السَّيْرُ جَمَعَ بَيْنَ الْمَغْرِبِ وَالْعِشَاءِ .
Ibn 'Umar reported: When the Messenger of Allah (ﷺ) was in a state of hurry on a journey, he combined the sunset and 'Isha' prayers.
Reference : Sahih Muslim 703aIn-book reference : Book 6, Hadith 52USC-MSA web (English) reference : Book 4, Hadith 1508