عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ رَضِيَ اللَّهُ عَنْهُ قَالَ: كُنَّا نُسَافِرُ مَعَ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ فَإِذَا صَعِدْنَا كَبَّرْنَا وَإِذَا هَبَطْنَا سَبَّحْنَا
Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) narrates that we used to travel with the Noble Prophet (peace and blessings be upon him). When we ascended (to a high place), we would say "Allahu Akbar," and when we descended (from a high place), we would say "Subhan Allah."