Anas bin Malik reported,

The Prophet ﷺ, when he set out on a journey before the sun had passed its zenith, would delay the noon prayer until the time of the afternoon prayer, then combine the two. But if the sun had already passed its zenith, he would pray the noon prayer first and then mount his ride.

Azami 2880

Sahih

عن أنس بن مالك قال

كان النبي ﷺ إذا ارتحل قبل أن تزيغ الشمس أخر الظهر إلى وقت العصر، ثم يجمع بينهما. وإذا زاغت صلى الظهر ثم ركب.

الأعظمي 2880صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Prayer
Chapter
Witr prayer
Section
Combining two prayers while traveling ﷺ
Numbering
Jami al-Kamil 2880 (2nd edition)
Azami 2880