仁王般若經疏 3.159

3.159

At that time, when the great assembly and the asura kings heard the Buddha speak of the seven terrifying calamities in future ages, their bodily hairs stood on end, and crying out in loud voices, they said: "We vow not to be born in those lands!" At that time, the sixteen great kings immediately entrusted the affairs of state to their younger brothers, renounced household life to practice the Path, contemplating the characteristics of transcendent mastery of the four great elements and the four colors, and the characteristics of meditative practices entering into the four great elements, the four colors, non-possession, consciousness, and space.