Musnad Ahmad 2:193

'Abd al-Rahman narrated to us, from Sufyan, from Ibrahim ibn 'Abd al-A'la, from Suwayd ibn Ghafala, who said: I saw 'Umar kissing the Stone, and he said: "I know indeed that you are a stone that neither harms nor benefits. But I saw Abu al-Qasim (may Allah bless him and grant him peace) being affectionate toward you."