Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrates from the Noble Prophet (peace and blessings be upon him) that he said: "When the Black Stone descended from Paradise, it was whiter than snow, then the sins of the people made it black."
Hadith Referenceصحيح ابن خزيمه / جماع أبواب ذكر أفعال اختلف الناس فى إباحته للمحرم، نصت سنة النبى صلى الله عليه وسلم أو دلت على إباحتها / 2733