SB 4.21.35

pradhāna-kālāśaya-dharma-saṅgrahe
 śarīra eṣa pratipadya cetanām
kriyā-phalatvena vibhur vibhāvyate
 yathānalo dāruṣu tad-guṇātmakaḥ
Word for word: 
pradhāna — material nature; kāla — time; āśaya — desire; dharma — occupational duties; saṅgrahe — aggregate; śarīre — body; eṣaḥ — this; pratipadya — accepting; cetanām — consciousness; kriyā — activities; phalatvena — by the result of; vibhuḥ — the Supreme Personality of Godhead; vibhāvyate — manifested; yathā — as much as; analaḥ — fire; dāruṣu — in the wood; tat-guṇa-ātmakaḥ — according to shape and quality.
Translation: 
The Supreme Personality of Godhead is all-pervading, but He is also manifested in different types of bodies which arise from a combination of material nature, time, desires and occupational duties. Thus different types of consciousness develop, just as fire, which is always basically the same, blazes in different ways according to the shape and dimension of firewood.
Purport: 

The Supreme Personality of Godhead constantly lives with the individual soul as Paramātmā. The individual soul has awareness in accord with his material body, which he attains by virtue of prakṛti, or material nature. The material ingredients are activated by the force of time, and thus the three material modes of nature are manifested. According to his association with the three modes of nature, the living entity develops a particular type of body. In animal life, the material mode of ignorance is so prominent that there is very little chance of realizing the Paramātmā, who is also present within the heart of the animal; but in the human form of life, because of developed consciousness (cetanām), one can be transferred from ignorance and passion to goodness by the results of his activities (kriyā-phalatvena). A human being is therefore advised to associate with spiritually advanced personalities. The Vedas (Muṇḍaka Upaniṣad 1.2.12) give the direction tad-vijñānārthaṁ sa gurum evābhigacchet: in order to reach the perfection of life or to understand the real constitutional position of the living entity, one must approach the spiritual master. Gurum evābhigacchet — one must; it is not optional. It is imperative that one approach the spiritual master, for by such association one proportionately develops his consciousness toward the Supreme Personality of Godhead. The highest perfection of such consciousness is called Kṛṣṇa consciousness. According to the body given by prakṛti, or nature, one’s consciousness is present; according to the development of consciousness, one’s activities are performed; and according to the purity of such activities, one realizes the Supreme Personality of Godhead, who is present in everyone’s heart. The example given herein is very appropriate: fire is always the same, but according to the size of the fuel or burning wood, the fire appears to be straight, curved, small, big, etc.

According to the development of consciousness, God realization is present. In the human form of life it is recommended, therefore, that one undergo the different types of penances and austerities described in Bhagavad-gītā (karma-yoga, jñāna-yoga, dhyāna-yoga and bhakti-yoga). Like a staircase, yoga has different steps for reaching the topmost floor, and according to one’s position upon the staircase, he is understood to be situated in karma-yoga, jñāna-yoga, dhyāna-yoga or bhakti-yoga. Of course, bhakti-yoga is the topmost step on the staircase of realization of the Supreme Personality of Godhead. In other words, according to one’s development in consciousness, one realizes his spiritual identity, and thus when one’s existential position is purified fully, he becomes situated in brahmānanda, which is ultimately unlimited. Therefore the saṅkīrtana movement contributed by the Supreme Personality of Godhead as Lord Caitanya is the direct and easiest process for coming to the purest form of consciousness — Kṛṣṇa consciousness, the platform on which the Supreme Personality is fully realized. Directions for performing different types of yajñas are specifically arranged for the highest realization of the Supreme Lord, as confirmed in Bhagavad-gītā by the Lord Himself. The Supreme Personality of Godhead is realized according to the proportion of one’s surrender: ye yathā māṁ prapadyante tāṁs tathaiva bhajāmy aham (Bg. 4.11). Full surrender, however, occurs when a man is perfectly in knowledge: bahūnāṁ janmanām ante jñānavān māṁ prapadyate (Bg. 7.19).