Riyad as-Salihin 975
Jabir (May Allah be pleased with him) reported:
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)."' [Al-Bukhari] .
عن جابر رضي الله عنه قال‏:‏ كنا إذا صعدنا كبرنا، وإذا نزلنا سبحنا‏.‏ ‏(‏‏(‏رواه البخاري‏)‏‏)‏‏.‏