Source: The Great Interpretation of Dreams (Ibn Sirin)
Eating ashes in a dream indicates false speech, unlawful money, or striving for a useless matter.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
Eating ashes indicates knowledge not acted upon, or worry and regret.
Source: Signs in the Science of Expressions (Ibn Shaheen)
Eating ashes is interpreted as worry and grief.