Sunan at-Tirmithiy كتاب الحج باب ما جاء فى فضل الحجر الأسود والركن والمقام
The Messenger of God, peace and blessings of God be upon him, said, "The Black Stone [1] descended from Paradise whiter than milk; the sins of the children of Adam then blackened it." Footnotes: [1] One of the stones comprising the southern corner of the Ka'bah. It marks the point at which people should start and end their circumambulation of the Ka'bah. It is of a special value to Muslims, as it is believed to have fallen from Heaven in the time of Adam and Eve. Click on ḥadīth to read more