Matsyapurana 47.12

47.12

naṣṭe dharme tathā jajñe viṣṇurvṛṣṇikule prabhuḥ
kartuṃ dharmasya saṃsthānam asurāṇāṃ praṇāśanam //

Lord Viṣṇu manifested Himself in the human form and deluded the world by His Yogic powers. Its history is that, when the earth became deprived of righteousness and the Asuras swelled the world, Lord Viṣṇu, in order to re-establish righteousness, incarnated Himself in the human form in the Vṛiṣṇi family.—11-12.