Sahih Bukhari Volume 2, Book 26, Hadith Number 696.

Narated By Abida bin Humaid : Abdul, Aziz bin Rufai Said, “I saw Abdullah bin Az-Zubair performing Tawaf of the Kaba after the morning prayer then offering the two Rakat prayer.” Abdul Aziz added, “I saw Abdullah bin Az-Zubair offering a two Rakat prayer after the Asr prayer.” He informed me that ‘Aisha told him that the Prophet used to offer those two Rakat whenever he entered her house.”