The body is the instrument of the Spirit or God. The Soul is a direct representative of the Spirit. The body needs the Soul to realise the Supreme, the Soul needs the body to manifest of glorify God on Earth. They complement each other. The Soul is part and parcel of God and as such immortal. It is the divine spark that gives the body life. When it leaves, the body dies. In my Book, My Guru Sri Chinmoy: Life and Teachings, there is a whole chapter dedicated to this. (Chapter 6) available from me or on amazon.com. Google and it will come up or write to me email@example.com. Much Peace.