Hadith 508180
Chapter 20: Hajj - كتاب الحج
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ هِشَامِ بْنِ عُرْوَةَ، أَنَّ أَبَاهُ، كَانَ إِذَا طَافَ بِالْبَيْتِ يَسْتَلِمُ الأَرْكَانَ كُلَّهَا وَكَانَ لاَ يَدَعُ الْيَمَانِيَ إِلاَّ أَنْ يُغْلَبَ عَلَيْهِ .
Yahya related to me from Malik from Hisham ibn Urwa that his father used to salute all the corners when he did tawaf of the House and did not omit the Yamani corner unless he was prevented from it.
Reference Muwatta Malik 508180
USC-MSA web (English) reference : Book 20, Hadith 115