Krishna offers one of the simplest analogies in the Gita. When wind passes through a flower garden, it picks up the fragrance and carries it along. We cannot see the wind, but we smell the flowers — and we know where the wind has been.
In exactly the same way, when the soul leaves one body and enters another, it carries along its inner impressions — the habits and tendencies of the mind and senses. The physical body is left behind, but the subtle patterns of thought, desire, and memory travel with the soul.
The soul is called 'ishvarah' here — the master of the body. This small word is significant. The soul is not a passive passenger. It is the conscious ruler of its own vehicle, actively carrying its accumulated nature from one life to the next.