Which corners (Arkaan) of the Kaaba should be touched (Istilam) during Tawaf?
Chapter on Mentioning Hajj and Entering Makkah
Al-Mughni
Book of Hajj
Primary text
The Black Stone corner (containing the Hajr al-Aswad) and the Yemeni corner (al-Rukn al-Yamani) must be touched in every circuit of the Tawaf. Evidence for this practice is established by the report of Ibn Umar stating that the Messenger of Allah (peace be upon him) never neglected to touch the Yemeni corner and the Black Stone in every Tawaf, a practice Ibn Umar himself maintained. The Yemeni corner is touched because it is built upon the foundations of Ibrahim (peace be upon him), similar to the Black Stone corner.
Supporting text
There is a difference of opinion regarding touching the two corners situated between the Black Stone and the Yemeni corner (the Iraqi and the Shami corners). The majority opinion holds that touching these two is not prescribed. However, a narration citing Mu'awiyah, Jabir, Ibn al-Zubayr, Al-Hasan, Al-Husayn, Anas, Urwah, and others supports touching all four corners, based on the statement that no part of the House should be forsaken. The counter-argument is based on the report that the Prophet (peace be upon him) only touched the Black Stone and the Yemeni corner, suggesting the other two were omitted because the House was not completed upon Ibrahim's foundations.