Reference : Hisn al-Muslim 234

طَافَ النَّبيُّ صلى الله عليه وسلم بِالْبَيْتِ عَلَى بَعِيرٍ كُلَّمَا أَتَى الرُّكْنَ أَشَارَ إِلَيْهِ بِشَيْءٍ عِنْدَهُ وَكَبَّرَ
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The Prophet (ﷺ) performed Tawaf 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: Allāhu 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.

Chapter: The Takbîr passing the black stone