(5) باب جَوَازِ الْجَمْعِ بَيْنَ الصَّلاَتَيْنِ فِي السَّفَرِ
Anas reported that when the Messenger of Allah (ﷺ) had to set out on a journey hurriedly, he delayed the noon prayer to the earlier time for the afternoon prayer, and then he would combine them, and he would delay the sunset prayer to the time when the twilight would disappear and then combine it with the 'Isha' prayer.
Reference: Sahih Muslim 704 c
In-book reference: Book 6, Hadith 58
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1514