Hazrat Salim bin Abdullah narrates from his esteemed father Sayyiduna Abdullah (may Allah be pleased with him), who says that the Messenger of Allah (peace and blessings be upon him) used to perform istilam (touching or kissing) of only the Hajar Aswad and the corner close to it on the side of Dar al-Jumhain (Rukn Yamani) among the corners of the Ka'bah.
Hadith Referenceصحيح ابن خزيمه / جماع أبواب ذكر أفعال اختلف الناس فى إباحته للمحرم، نصت سنة النبى صلى الله عليه وسلم أو دلت على إباحتها / 2725