Hadith 2587
وَفِي رِوَايَةٍ لَهُمَا: قَالَ نَافِعٌ: رَأَيْتُ ابْنَ عُمَرَ يَسْتَلِمُ الْحَجَرَ بِيَدِهِ ثُمَّ قَبَّلَ يَدَهُ وَقَالَ: مَا تَرَكْتُهُ مُنْذُ رَأَيْتُ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَفْعَله
In a version by both of them Nafi’ said he saw Ibn ‘Umar touching the stone with his hand, after which he kissed his hand. He said, “I have not given it up since I saw God's messenger doing it." Bukhari and Muslim.