Now what are the occasions which lead to these great manifestations? None can speak with mightier authority on this point than He who came Himself as an Avatâra just before the beginning of our own age, the Divine Lord Shrî Kṛiṣhṇa Himself. Turn to that marvellous poem, the Bhagavad-Gîtâ, to the fourth Adhyâya, Shlokas 7 and 8; there He tells us what draws Him forth to birth into His world in the manifested form of the Supreme:
यदा यदाहिधर्मस्य घ्लानिर्भवति भारत ।
अभ्युत्थानमधर्मस्य तदात्मानं सृजाम्यहम् ॥
परित्राणाय साधूनाम् विनासायचदुष्कृताम् ॥
धर्मसंस्धापनार्थाय संभवामि युगे युगे ॥
[Sanskrit:
yadA yadAhidharmasya GlAnirBavati BArata |
aByutthAnamadharmasya tadAtmAnaM sRujAmyaham ||
paritrANAya sAdhUnAm vinAsAyacaduShkRutAm ||
dharmasaMsdhApanArthAya saMBavAmi yuge yuge ||]