Yahya related to me from Malik from Jafar ibn Muhammad ibn AIifrom his father that Jabir ibn Abdullah said, "I heard the Messengerof Allah, may Allah bless him and grant him peace, say as he left themosque, intending to go to Safa, 'We begin with that with which Allahbegan,' and he began with Safa."
USC-MSA web (English) reference: Book 20, Hadith 127
Arabic reference: Book 20, Hadith 830