Ramayana
यद्यसौ तप आतिष्ठेद्भूय एवासुरेश्वर । यावल्लोका धरिष्यन्ति तावदस्य वशानुगाः ॥ 7-84-13 ॥
"'If he, O lord of the asuras, should perform austerity yet further, then for as long as the worlds shall endure, they will remain subject to his will."
english translation