The name of the battle between the Aus and the Khazraj, the two pagan tribes in Yathrub/ Madina.

Sahih Al-Bukhari HadithHadith 5.186        Narrated byAisha
Allah Caused the day of Buath to take place before Allah's Apostle was sent (as an Apostle) so that when Allah's Apostle reached Medina, those people had already divided (in different groups) and their chiefs had been killed or wounded. So Allah made that day precede Allah's Apostle so that they (i.e. the Ansar) might embrace Islam.
Narrated 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."