Sahih Bukhari | Volume 5 | Hadith Number 670

Narrated by Abu Masud
The Prophet beckoned with his hand towards Yemen and said, "Belief is there." The harshness and mercilessness are the qualities of those farmers etc, who are busy with their camels and pay no attention to the religion (is towards the east) from where the side of the head of Satan will appear; those are the tribes of Rabi'a and Mudar.