Without the singular number.

1. The earthy particles of combustible substances remaining after combustion; as of wood or coal.

2. The remains of the human body when burnt. Hence figuratively, a dead body or corpse.

3. In scripture, ashes is used to denote vileness, meanness, frailty, or humiliation.

I who am but dust and ashes. Genesis 18:27.

I abhor myself and repent in dust and ashes. Job 42:6.