Merits of the Helpers in Madinah (Ansaar)
وَقَالَ ابْنُ وَهْبٍ أَخْبَرَنَا عَمْرٌو، عَنْ بُكَيْرِ بْنِ الأَشَجِّ، أَنَّ كُرَيْبًا، مَوْلَى ابْنِ عَبَّاسٍ حَدَّثَهُ أَنَّ ابْنَ عَبَّاسٍ ـ رضى الله عنهما ـ قَالَ لَيْسَ السَّعْىُ بِبَطْنِ الْوَادِي بَيْنَ الصَّفَا وَالْمَرْوَةِ سُنَّةً، إِنَّمَا كَانَ أَهْلُ الْجَاهِلِيَّةِ يَسْعَوْنَهَا وَيَقُولُونَ لاَ نُجِيزُ الْبَطْحَاءَ إِلاَّ شَدًّاNarrated Ibn 'Abbas:To run along the valley between two green pillars of Safa and Marwa (mountains) was not Sunna, 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
From Sahih al-Bukhari, whose reports the scholars accept as authentic.