The Book of Prayer - Travellers
6/5. Chapter:
It is permissible to combine two prayers when traveling
Sahih Muslim
وَحَدَّثَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، حَدَّثَنَا يَحْيَى، عَنْ عُبَيْدِ اللَّهِ، قَالَ أَخْبَرَنِي نَافِعٌ، أَنَّ ابْنَ عُمَرَ، كَانَ إِذَا جَدَّ بِهِ السَّيْرُ جَمَعَ بَيْنَ الْمَغْرِبِ وَالْعِشَاءِ بَعْدَ أَنْ يَغِيبَ الشَّفَقُ وَيَقُولُ إِنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ إِذَا جَدَّ بِهِ السَّيْرُ جَمَعَ بَيْنَ الْمَغْرِبِ وَالْعِشَاءِ .
Nafi' reported that when Ibn 'Umar was in a state of hurry on a journey, he combined the sunset and 'Isha' prayers after the twilight had disappeared, and he would say that 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 703bIn-book reference : Book 6, Hadith 53USC-MSA web (English) reference : Book 4, Hadith 1509