عن جابر رضي الله عنه
قال: كنا إذا صعدنا كبرنا، وإذا نزلنا سبحنا
When we ascended (a height) we would proclaim: “Allahu Akbar (Allah is Greatest),” and when we descended (from the height) we would proclaim: “Subhan Allah (Allah is free from imperfection).”.
Riyad as-Salihin 975, Book 8, The Book of Etiquette of Traveling, Hadith 20. 1 min read