Sahih al-Bukhari, Book 25, Hadith 96 (In-Book) ⓘ
Narrated Zaid bin Aslam that his father said: "I saw `Umar bin Al-Khattab kissing the Black Stone and he then said, (to it) 'Had I not seen Allah's Apostle kissing you, (stone) I would not have kissed you.' "
حَدَّثَنَا أَحْمَدُ بْنُ سِنَانٍ، حَدَّثَنَا يَزِيدُ بْنُ هَارُونَ، أَخْبَرَنَا وَرْقَاءُ، أَخْبَرَنَا زَيْدُ بْنُ أَسْلَمَ، عَنْ أَبِيهِ، قَالَ رَأَيْتُ عُمَرَ بْنَ الْخَطَّابِ ـ رضى الله عنه ـ قَبَّلَ الْحَجَرَ وَقَالَ لَوْلاَ أَنِّي رَأَيْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم قَبَّلَكَ مَا قَبَّلْتُكَ.
also referenced under: Hadith 1610 (DarusSalam) & Volume 2, Book 26, Hadith 679 (USC-MSA)