CC Madhya 19.140
jivaḥ sūkṣma-svarūpo ’yaṁ
saṅkhyātīto hi cit-kaṇaḥ
keśa-agra — of the tip of a hair; śata-bhāgasya — of one hundredth; śata-aṁśa — a hundredth part; sadṛśa — equal to; ātmakaḥ — whose nature; jīvaḥ — the living entity; sūkṣma — very fine; svarūpaḥ — identification; ayam — this; saṅkhya-atītaḥ — numbering beyond calculation; hi — certainly; cit-kaṇaḥ — spiritual particle.
“ ‘If we divide the tip of a hair into a hundred parts and then take one of these parts and divide it again into a hundred parts, that very fine division is the size of but one of the numberless living entities. They are all cit-kaṇa, particles of spirit, not matter.’
This is quoted from the commentary on the portion of Śrīmad-Bhāgavatam wherein the Vedas personified offer their obeisances unto the Supreme Personality of Godhead. Lord Kṛṣṇa confirms this statement in the Bhagavad-gītā (15.7): mamaivāṁśo jīva-loke jīva-bhūtaḥ sanātanaḥ. “The living entities in this conditioned world are My eternal fragmental parts.”
Lord Śrī Kṛṣṇa personally identifies Himself with the minute living entities. Lord Kṛṣṇa is the supreme spirit, the Supersoul, and the living entities are His very minute parts and parcels. Of course, we cannot divide the tip of a hair into such fine particles, but spiritually such small particles can exist. Spiritual strength is so powerful that a mere atomic portion of spirit can be the biggest brain in the material world. The same spiritual spark is within an ant and within the body of Brahmā. According to his karma, material activities, the spiritual spark attains a certain type of body. Material activities are carried out in goodness, passion and ignorance or a combination of these. According to the mixture of the modes of material nature, the living entity is awarded a particular type of body. This is the conclusion.