Umar ibn al-Khattāb (may Allah be pleased with him) reported that he came to the Black Stone and kissed it and said: ""Verily, I know that you are a stone that can neither benefit nor harm. Had I not seen the Prophet (may Allah's peace and blessings be upon him) kissing you, I would not have kissed you. [Sahih/Authentic] - [Al-Bukhari and Muslim

"عن عمر بن الخطاب -رضي الله عنه- «أنَّه جَاء إِلى الحَجَر الأَسوَدِ، فَقَبَّلَه، وقال: إِنِّي لَأَعلَم أَنَّك حَجَرٌ، لا تَضُرُّ ولا تَنفَعُ، ولَولاَ أَنِّي رَأَيتُ النبيَّ -صلَّى الله عليه وسلَّم- يُقَبِّلُك مَا قَبَّلتُك». [صحيح.] - [متفق عليه.]"