Mishkat al-Masabih 10 The Rites of Pilgrimage كتاب المناسك 82

وَعَنْ عَابِسِ بْنِ رَبِيعَةَ قَالَ: رَأَيْت عمر يقبل الْحجر وَيَقُول: وَإِنِّي لَأَعْلَمُ أَنَّكَ حَجَرٌ مَا تَنْفَعُ وَلَا تَضُرُّ وَلَوْلَا أَنِّي رَأَيْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يقبل مَا قبلتك

‘Abis b Rabi’a said he saw ‘Umar kissing the stone and saying, “I know for sure that you are a stone which can neither benefit nor injure, and had I not seen God’s messenger kissing you I would not have kissed you.” (Bukharl and Muslim.)