A tribe is a group of clans that belong to, or have invented for themselves, one ancestor for the purpose of preserving their unity and cohesion, and gathered around water and pasture, to live on herding, hunting and raiding, inventing for themselves a custom that they have come to know and agree upon, or a “tribal law” that regulates aspects of their internal life, and their relationships with other tribes, from neighboring, alliance, enmity and hostility, and other relationships.