According to the desires of the living being, the material body develops. So from the spirit soul the material body comes into existence, generated from the living force
SB Canto 2
The Personality of Godhead is the supreme master of everything auspicious because the results of whatever actions are performed by the living being, in either the material or spiritual existence, are awarded by the Lord. As such, He is the ultimate benefactor. Every individual living entity is unborn, and therefore even after the annihilation of the material elementary body, the living entity exists, exactly like the air within the body.
The living entity is unborn and eternal, and as confirmed in the Bhagavad-gītā (2.30), the living entity is not exhausted even though the material elementary body is vanquished. As long as the living entity is in material existence, actions performed by him are rewarded in the next life, or even in the present life. Similarly, in his spiritual life also actions are rewarded by the Lord by the five kinds of liberation. Even the impersonalist cannot achieve the desired merging into the existence of the Supreme without being favored by the Supreme Personality of Godhead. It is confirmed in the Bhagavad-gītā (4.11) that the Lord awards similar results, as one desires, in one's present life. The living entities are given freedom to make their choice, and the Lord awards them accordingly.
It is the duty of everyone, therefore, to worship devoutly only the Personality of Godhead to achieve his desired goal. The impersonalist, instead of speculating or meditating, can directly execute the routine devotional service of the Lord and thus easily obtain the desired goal.
The devotees, however, are naturally inclined to become associates of the Lord and not merge in the spiritual existence, as conceived by the impersonalist. The devotees, therefore, following their constitutional instincts, achieve the desired goal of becoming servitors, friends, fathers, mothers or conjugal lovers of the Lord. The devotional service of the Lord involves nine transcendental processes, such as hearing and chanting, and by performing such easy and natural devotional services the devotees achieve the highest perfectional results, far, far superior to merging into the existence of Brahman. The devotees are therefore never advised to indulge in speculating upon the nature of the Supreme or artificially meditating on the the void.
One should not, however, mistakenly think that after the annihilation of this present body there is no body by which one can associate with the Lord face to face. The living entity is unborn. It is not that he is manifest with the creation of the material body. On the other hand, it is true that the material body develops only by the desire of the living entity. The evolution of the material body is due to the desires of the living being. According to the desires of the living being, the material body develops. So from the spirit soul the material body comes into existence, generated from the living force. Since the living being is eternal, he exists just like the air within the body. Air is within and without the body. Therefore when the external covering, the material body, is vanquished, the living spark, like the air within the body, continues to exist. And by the direction of the Lord, because He is the ultimate benefactor, the living entity is at once awarded the necessary spiritual body befitting his association with the Lord in the manner of sārūpya (equal bodily feature), sālokya (equal facility to live on the same planet with the Lord), sārṣṭi (equal possession of opulence like the Lord), and sāmīpya (equal association with the Lord).
The Lord is so kind that even if a devotee of the Lord cannot fulfill the complete course of devotional service unalloyed and uncontaminated by material association, he is given another chance in the next life by being awarded a birth in the family of a devotee or rich man so that without being engaged in the struggle for material existence the devotee can finish the remaining purification of his existence and thus immediately, after relinquishing the present body, go back home, back to Godhead. This is confirmed in the Bhagavad-gītā.
In this connection detailed information is available in the Bhagavat-sandarbha of Śrīla Jīva Gosvāmī Prabhupāda. Once achieving the spiritual existence, the devotee is eternally situated there, as already discussed in the previous verse.