وَعَنِ ابْنِ عُمَرَ
قَالَ: لَمْ أَرَ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَسْتَلِمُ من الْبَيْت إِلَّا الرُّكْنَيْنِ اليمانيين
He had not seen the Prophet (sallallahu alayhi wa sallam) touching anything in the House but the two Yamani corners (The corner containing the Black Stone and the Yamani corner to the south-east which, as is usually held, should be touched but not kissed. They are both held to be on the foundations laid by Abraham). Bukhari and Muslim.
Mishkat al-Masabih 2460, Book 11, The Rites of Pilgrimage, Hadith 62. 1 min read