Chapter 4 - Verse 7

यदा यदा हि धर्मस्य ग्लानिर्भवति भारत ।
अभ्युत्थानमधर्मस्य तदाऽऽत्मानं सृजाम्यहम् ॥ ७ ॥

yadā yadā hi dharmasya glānirbhavati bhārata .
abhyutthānamadharmasya tadā’’tmānaṃ sṛjāmyaham .. 7 ..


Whenever there is a decay of religion, O Bhārata, and an ascendency of irreligion, then I manifest Myself.
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Religion: Dharma as embodied in the institution of castes (varna) and religious orders (asrama) which are the means of attaining worldly prosperity and salvation. Whenever there is a decay of religion (Dharma),……..I manifest Myself through Māyā.

For what purpose?