In so many different ways, Krsna is convincing how the spirit soul is immortal. In different ways. Avyakto 'yam. It is not manifest to the blunt material eyes. We cannot see. Because as we have explained several times, the magnitude of the soul is one ten-thousandth part of the tip of the hair, very small. I think, smaller than the atom. That spirit soul is everywhere. Sarva-ga. Sarva-gata. Everywhere. Andantara-stha-paramanu-cayantara-stham [Bs. 5.35]. And wherever the spirit soul is there within this material world, he has got a body and there is heart, and within that heart, Krsna is also there. Isvarah sarva-bhutanam hrd-dese arjuna tisthati [Bg. 18.61]. Both of them, living there. Therefore anor aniyan mahato mahiyan. Krsna can become greater than the greatest and the smaller than the smallest. This is God.
Lecture on Bhagavad-gita 2.25, Hyderabad, 29 November, 1972