"Although I am unborn and inexhaustible, and although I am the Lord of all beings,

 

"Although I am unborn and inexhaustible, and although I am the Lord of all beings, keeping nature under My control, I manifest Myself by My own self induced illusion (maya). Whenever and wherever there is decline of dharma (righteousness) and ascendance of adharma (unrighteousness), at that time I manifest Myself in visible form . For the protection of the righteous and destruction of the wicked, and for the sake of establishing dharma again, I incarnate Myself on earth from time to time."

Lord Sri Krishna