It is narrated from Sayyiduna Abu Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) once pointed with his blessed hand towards Yemen and said: "Iman (faith) is here. Beware! Harshness and severity of hearts are found among those arrogant ones who are the owners of camels, from where the horn of Satan appears." That is, among the tribes named Rabi'ah and Mudar.