The body is a temporary machine; the soul eternally yearns for spiritual bliss with Krishna.Listen — Srila Prabhupada Uvaca
Śrīmad-Bhāgavatam 3.26.29 — January 6, 1975, Bombay 750106SB-BOMBAY [33:28 Minutes] SB-03.26.29_750106SB-BOMBAY Nitāi: Oṁ namo bhagavate vāsudevāya. [devotees repeat] [leads chanting of verse, etc.] taijasāt tu vikurvāṇād buddhi-tattvam abhūt sati dravya-sphuraṇa-vijñānam indriyāṇām anugrahaḥ [SB 3.26.29] [01:34] "By the transformation of the false ego in passion, intelligence takes birth, O virtuous lady. The functions of the intelligence are to help in ascertaining the nature of objects when they come into view, and to help the senses." Prabhupāda: taijasāt tu vikurvāṇād buddhi-tattvam abhūt sati dravya-sphuraṇa-vijñānam indriyāṇām anugrahaḥ [SB 3.26.29] So these things are taking place daily within the womb of the mother—how the child is developing from the day of union of the father and the mother, and on the first day it is like a pealike form by the semina of father and mother, and then everything develops. Different types of body, different types of intelligence, different types of brain—how it takes place?
If it is simply material, then all children would have come out of the same quality. But it does not so come. Every child, baby, born has got everything separate from the others. How subtle laws of nature is working, we can just imagine.
It is not possible to understand by our these material senses even this material formation of the body, what to speak of spiritual understanding. Therefore, in the śāstras it is advised, acintyāḥ khalu ye bhāvā na tāṁs tarkeṇa yojayet [Mahābhārata, Bhīṣma-parva 5.22]. Acintyāḥ khalu ye bhāvāḥ. Things which are beyond your perception, sense perception, acintya, mental speculation, not cintanīya... Acintya.
Acintya means mentally speculating. Beyond that, acintya, you cannot think of how this pealike form develops into such a big brain or small brain. The hands, legs and the mechanical process of different body... This is a machine.
In the material world we manufacture machine, manufacturing different parts and assembling them. [child makes noises] [aside:] The child may be... But this machine is automatically developing. There is no question of manufacturing each part and then assembling.
It is yantra. This body is yantra, machine. That is stated in the Bhagavad-gītā: īśvaraḥ sarva-bhūtānāṁ hṛd-deśe 'rjuna tiṣṭhati bhrāmayan sarva-bhūtāni yantrārūḍhāni māyayā [Bg. 18.61] Īśvara, the Supreme Personality of Godhead, is situated in everyone's heart. He is supervising what kind of yantra, or machine, this living entity requires for fulfilling his desires.
That is karma. He is engaged in such karma, and he is manufacturing by his karma another body. Everything is going on by the laws of nature. Prakṛteḥ kriyamāṇāni guṇaiḥ karmāṇi sarvaśaḥ [Bg. 3.27].