What is the number of warriors that participated in the Battle of Badr as mentioned in a hadith narrated by Al-Bara which is the same number of Companions of Prophet Muhammad (saw) that crossed the river with him?
 Narrated Al-Bara:                     We used to say that the warriors of Badr were over three-hundred-and-ten, as many as the Companions of Saul who crossed the river with him; and none crossed the river with him but a believer.