سُنَنُ النَّسَائِيِّ
Sunan an-Nasa’i 598
The Book of the Times (of Prayer)
Situations During Which It Is Permissible To Combine Two Prayers
أَخْبَرَنَا قُتَيْبَةُ بْنُ سَعِيدٍ، عَنْ مَالِكٍ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ إِذَا جَدَّ بِهِ السَّيْرُ جَمَعَ بَيْنَ الْمَغْرِبِ وَالْعِشَاءِ .
It was narrated from Ibn 'Umar that if the Messenger of Allah (ﷺ) was in a hurry to travel, he would combine Maghrib and 'Isha'.
Sunan an-Nasa'i, 598Sahih (Darussalam)