What did Prophet Muhammad (saw) do each time he reached the corner of the Black Stone during the Tawaf (circling the Ka'ba)?
 Narrated Ibn `Abbas:                     Allah's Apostle performed the Tawaf (around the Ka`ba while riding his camel, and every time he reached the corner (of the Black Stone) he pointed at it with his hand and said, "Allahu Akbar." (Zainab said: The Prophet said, "An opening has been made in the wall of Gog and Magog like this and this," forming the number 90 (with his thumb and index finger).