Sahih Bukhari Volume 001, Book 003, Hadith Number 128.
Narated By Aswad : Ibn Az-Zubair said to me, "'Aisha used to tell you secretly a number of things. What did she tell you about the Ka'ba?" I replied, "She told me that once the Prophet said, 'O 'Aisha! Had not your people been still close to the pre-Islamic period of ignorance (infidelity)! I would have dismantled the Ka'ba and would have made two doors in it; one for entrance and the other for exit." Later on Ibn Az-Zubair did the same.