What does it mean that "the sky is the coffin cover, the earth is the coffin board, and all the joys and sorrows are in the coffin"?

Life and death, life and death, life and death, husband and death. If a person lives without a soul, he is like a walking corpse. What is the difference between him and the dead?

In fact, in this world, the sky is the coffin cover and the earth is the coffin plate. People live and multiply in this huge coffin, and the soul endures joys and sorrows.

All people have life and death, because we all live in coffins, and we can't escape God's doomed fate.