The Black Stone (Hajr Aswad)
The Messenger of Allah (peace and blessings of Allah be upon him) said: “The Black Stone came down from Paradise and it was whiter than milk, but the sins of the sons of Adam turned it black.” [Narrated by al-Tirmidhi]
The Black Stone is set in the one of the Southern corners of the Ka’bah. It is a blessed stone from one of the stones of Paradise. The Prophet (SAW) touched it and kissed it when starting each round of Tawaf (circumambulation) of the House and therefore we are also commanded to touch it and kiss it if possible.
Due to the large number of pilgrims, in most cases, it is almost impossible to touch and kiss the Black Stone unless you push and shove your way through. It is sufficient to just raise your hands to it, kiss the hands and start the Tawaf by saying Bismillah Allahu Akbar.
When the Black Stone came down from Paradise it was a white as milk, but it soon turned black due to the sins of Mankind.
It is currently in a silver casing because it was stolen by a heretical group called the Qarmatians in the middle ages and was broken to pieces before being recovered by the Caliph. The silver casing is there to hold all the broken pieces together.
The Black Stone will come with eyes and a tounge on the day of Judgement and will intercede to Allah on behalf of everyone that touched it and kissed it.