"I have not seen the Prophet (ﷺ) touching except the two Yemenite Corners (i.e. the ones facing Yemen)."
Sahih al-Bukhari Book 25, Hadith 95
← Previous Hadith Abu Ash-Sha'tha said, "Who keeps away from some portion of the Ka'bah?" Mu'awiya used to touch the four corners of the Ka'bah, Ibn 'Abbas said to him, "These two corners (the one facing the Hijr) are not to be touched." Mu'awiya said, "Nothing is untouchable in the Ka'bah." And Ibn Az-Zubair used to touch all the corners of the Ka'bah.

Sahih al-Bukhari Book 25, Hadith 94 Next Hadith → "I saw `Umar bin Al-Khattab kissing the Black Stone and he then said, (to it) 'Had I not seen Allah's Apostle kissing you, (stone) I would not have kissed you.' "

Sahih al-Bukhari Book 25, Hadith 96