Narrated Ibn Abbas (Radi-Allahu 'anhu):

Allah's Apostle (Sallallahu 'Alaihi Wa Sallam) performed Tawaf (of the
Kaba) ending a camel (at that time the Prophet (Sallallahu 'Alaihi Wa
Sallam) had foot injury). Whenever he came to the Corner (having the Black
Stone) he would point out towards it with a thing in his hand and say,
"Allahu-Akbar."

Bukhari Vol. 2 : No. 697