The funereal phrase is "earth to earth, ashes to ashes, dust to dust."
(Bartleby) NUMBER: 10398
AUTHOR: Book of Common Prayer
QUOTATION: Earth to earth, ashes to ashes, dust to dust, in sure and certain hope of the resurrection.
ATTRIBUTION: The Burial Service.
Ashes and dust are an important part of Christian and Jewish symbolism. They are signs of repentence and a knowledge of your sins. Ashes can also be used, therefore, in ritually cleansing.
Ash Wednesday is the day when good Catholics receive the sign of the cross on the forehead, drawn in ashes from the previous year's burning of the palms from Palm Sunday. Many burial services will include a bucket of ash that has been blessed with the intention of being used for ritual purposes.