"to reflect that dust he was"
Elohim Creating Adam (1795)
Public DomainElohim Creating Adam (1795) - Credit: William Blake

An allusion to the Creation myth recounted in Genesis whereby God created mankind out of the dust of the earth. God would subsequently decree, upon casting Adam and Eve out of the garden of Eden, that with death mankind would return to the dust from whence he came:

In the sweat of thy face shalt thou eat bread, till thou return unto the ground; for out of it wast thou taken: for dust thou art, and unto dust shalt thou return.

Genesis 3:19 (King James Bible)

 

All go unto one place; all are of the dust, and all turn to dust again.

Ecclesiastes 3:20 (King James Bible)