Sahih Bukhari
Pilgrimmage (Hajj)
Volume: 002 / Book Number: 026 / Hadith Number: 667
Narrated 'Abis bin Rabia:
'Umar came near the Black Stone and kissed it and said "No doubt, I know that you are a stone and can neither benefit anyone nor harm anyone. Had I not seen Allah's Apostle kissing you I would not have kissed you."