Saying Allahu 'Akbar when passing the Black Stone
 

234. The Prophet (SAW) performed At-Tawaaf riding a camel. Every time he passed the corner (containing the Black Stone), he would point to it with something that he was holding and say: 

اللهُ أكْبَر

Allaahu 'Akbar 

Allah is the Most Great!

Reference: Al-Bukhari, cf. Al-Asqalani, Fathul-Bari 3/476. See also 472. The 'something' that was referred to in this Hadith was a cane