Authentic Supplication Number 197.

In another respect: The Messenger of Allah  and his companions were such that if they were ascending mountain passages they would make Takbeer [ say ‘Allahu ‘akbaru (215)] and if they were descending they would make Tasbeeh [say Subhana ‘allahi (216)].

(215) Meaning Allah is greater [than everything].
(216) Meaning Glorified is Allah and removed from any imperfections.

Al-Albani said that it was reported, with two or more narrators in succession missing from its chain, by way of Ibn Juraij in Sunan ‘Abi Dawood. He said that it was merged into hadeeth #196 which Muslim reported by way of ‘Ibn `Umar. Al-Albani pointed out that Ibn Hajar said it was among the most precise [difficult to detect] mergings into a hadeeth. Merging is the addition of explanatory comments which are not part of the hadeeth into the hadeeth by one of its narrators. Al-Albani said that this hadeeth was similarly reported in Saheeh ‘Al-Bukhari. The wording was like this: “We used to when climbing make Takbeer, and when descending make Tasbeeh.” Al-Albani included this hadeeth in The Authentic of Good Sayings as #140.