To fully grasp the concept of death in Sikhism one must first understand the true nature of man and the purpose of birth and life in this world:
‘O my mind, thou art a Spark of Divine Light,
realise thy true Essence.
By realising thy true nature, thou graspest
that of God,
And thus knowest thou the mystery of birth and death. (SGGS p. 441)
‘Man’s body is made of walls of water, pillars of air and mud of blood - drops.
In the cage of bones, flesh and blood vessels abides the poor bird of life (soul)’. (SGGS p. 659)
This spirit or the soul is the real self and is a part and parcel of the Universal Soul (God). The individual self is Divine in Essence but not in itself the Infinite:
‘O my body, the Lord put His Divine Spark in thee
and so thou camest into the world;
Thou camest into the world when the Lord illumined
thy mind with His Divine Light.’ (SGGS:921)