Sahih Muslim | Book 1 | Hadith Number 83

Narrated by Ibn Mas'ud
It is narrated on the authority of Ibn Mas'ud that the Apostle of Allah (may peace and blessings be upon him) pointed towards Yemen with his hand and said: Verily Iman is towards this side, and harshness and callousness of the hearts is found amongst the rude owners of the camels who drive them behind their tails (to the direction)where emerge the two horns of Satan, they are the tribes of Rabi'a and Mudar.