حَدَّثَنَا وَكِيعٌ عَنْ هِشَامٍ عَنْ أَبِيهِ أَنَّ عُمَرَ رَضِيَ اللَّهُ عَنْهُ أَتَى الْحَجَرَ فَقَالَ إِنِّي لَأَعْلَمُ أَنَّكَ حَجَرٌ لَا تَضُرُّ وَلَا تَنْفَعُ وَلَوْلَا أَنِّي رَأَيْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يُقَبِّلُكَ مَا قَبَّلْتُكَ قَالَ ثُمَّ قَبَّلَهُ
مسند امام احمد بن حنبل · Hadith 381
It was narrated from Hisham, from his father, that 'Umar (RA) came to the [Black] Stone and said: i know that you are only a stone and you cannot cause harm or bring benefit. Were it not that I saw the Messenger of Allah (PBUH) kiss you, I would not have kissed you. Then he kissed it.