Sahih Bukhari Volume 2, Book 25, Hadith 1607

حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، عَنْ عُبَيْدِ اللَّهِ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ ـ رضى الله عنهما ـ قَالَ مَا تَرَكْتُ اسْتِلاَمَ هَذَيْنِ الرُّكْنَيْنِ فِي شِدَّةٍ وَلاَ رَخَاءٍ، مُنْذُ رَأَيْتُ النَّبِيَّ صلى الله عليه وسلم يَسْتَلِمُهُمَا‏.‏ قُلْتُ لِنَافِعٍ أَكَانَ ابْنُ عُمَرَ يَمْشِي بَيْنَ الرُّكْنَيْنِ قَالَ إِنَّمَا كَانَ يَمْشِي لِيَكُونَ أَيْسَرَ لاِسْتِلاَمِهِ‏

Narrated By Nafi' : Ibn 'Umar. said, "I have never missed the touching of these two stones of Ka'ba (the Black Stone and the Yemenite Corner) both in the presence and the absence of crowds, since I saw the Prophet touching them." I asked Nafi': "Did Ibn 'Umar use to walk between the two Corners?" Nafi' replied, "He used to walk in order that it might be easy for him to touch it (the Corner Stone)."