When the spirit soul reincarnates from one material body to another, does the Supreme Soul (God) accompany it?

Yes, when the spirit soul reincarnates from one material body to another, the Supreme Soul, none other than Krishna, the Supreme Personality of Godhead, accompanies it.

In truth, the incarnated spirit soul resides deep within the heart of a material body—human, animal, or plant. Both the Supreme Soul and the individual soul come into the same gross material body.

The Supreme Soul is called a Friend because Krishna, the Supreme Personality of Godhead, shows such kindness to the individual soul (which each of us truly is) that He accompanies it when it reincarnates from one material body to another. Furthermore, the Lord, through the material energy, His agent, creates a new body for him according to his desires and karma.

The heart plays a mechanical role in the body, as God explains in these words: The Lord resides in the hearts of all beings and directs their wanderings, each of whom is as if on a machine made of material energy.

Indeed, the driver of the body that God calls a “machine” is the individual soul, which is also its master and owner, but the supreme owner is none other than Krishna, the Supreme Personality of Godhead.

A person's body is created through the material energy of Godhead, through specific parents (celestial beings, human beings, or animals), and depending on the person's activities during their current life, another body will be created for them, always under the direction of the material energy, which acts under the authority of Krishna, the Supreme Personality of Godhead.

When the time comes, our next body is immediately determined, and the individual soul, along with the Supreme Soul, is transported into the new “machine,” the new body. This is how reincarnation takes place.

During the transfer from one material body to another, the individual spirit soul is carried away by the servants of Yamaraja, the master of death and judge of sinners, appointed to this position by God. They first make it pass through a certain type of hellish life so as to accustom it to the condition it will experience in its next body.