Sahih Imam Bukhari Volume 5, Book 58, Number 186 …Narrated Ibn ‘Abbas: To run along the valley between two green pillars (idols) of Safa (Isaf) and Marwa (Naila) was not sunna (tradition), but the people in the pre-Islamic period of ignorance used to run along it, and used to say: “We do not cross this rain stream except running strongly. ”