4-7

यदा यदा हि धर्मस्य ग्लानिर्भवति भारत ।
अभ्युत्थानम् अधर्मस्य तदात्मानम् सृजाम्यहम् ॥ ७ ॥

yadA yadA hi dharmasya glAnirbhavati bhArata |
abhyutthAnam adharmasya tadAtmAnam sRjAmyaham || 7 ||

यदा यदा [yadA yadA] Whenever धर्मस्य ग्लानिर्भवति [dharmasya glAnirbhavati] principles are subverted अभ्युत्थानम् [abhyutthAnam] and there is increase in अधर्म [adharma] vice, अहम् आत्मानम् [aham AtmAnam] I make Myself सृजामि [sRjAmi] come into being तदा [tadA] at that point in time.

My birth is not time-bound. The Vedas lay down principles that apply to the four professions (study, administration, trade and service) and the four stages in life (student, householder, retreat, renunciation). These principles are part of ‘dharma’. When they are subverted and factors that are opposed to them get the upper hand, I Myself come into being. I come into being by My own will, in the manner described before.

Next, He describes the purpose of his birth