Riyad as-Salihin

'Abis bin Rabi'ah (May Allah be pleased with him) reported: I saw 'Umar bin Al-Khattab (May Allah be pleased with him) kissing the Black Stone (Al-Hajar Al-Aswad) and saying: "I know that you are just a stone and that you can neither do any harm nor give benefit. Had I not seen Messenger of Allah (ﷺ) kissing you, I would not have kissed you".

[Al-Bukhari and Muslim].