Did Allah's Messenger (ﷺ) observe prayer in it? He said: Yes, he observed prayer between these two Yemenite pillars (pillars situated towards the side of Yemen).
Sahih Muslim Book 15, Hadith 439
← Previous Hadith Where did Allah's Apostle (ﷺ) observe prayer? They said: At this very place. I, however, forgot to ask them about the (number of) rak'ahs that he observed.

Sahih Muslim Book 15, Hadith 438 Next Hadith → I saw Allah's Messenger (ﷺ) entering the Ka'ba, and Usama b. Zaid, Bilal and 'Uthman b. Talha were along with him, but none (else) entered therein along with them. Then the door was closed for them from within. 'Abdullah b. Umar (Allah be pleased with them) said: Bilal and Uthman b. Talha informed me that Allah's Messenger (ﷺ) observed prayer in the interior of the Ka'ba between the two Yemenite pillars.

Sahih Muslim Book 15, Hadith 440