Sahih Bukhari Volume 6, Book 60, Hadith Number 376.

Narrated By Um Salama : I complained to Allah’s Apostle that I was sick, so he said, “Perform the Tawaf (of Ka’ba at Mecca) while riding behind the people (who are performing the Tawaf on foot).” So I performed the Tawaf while Allah’s Apostle was offering the prayer by the side of the Ka’ba and was reciting: ‘By the Mount (Saini) and by a Decree Inscribed.”