The cross of ashes, traced upon the forehead of each Christian, is not only a reminder of death but inevitably (though tacitly) a pledge of resurrection. The ashes of a Christian are no longer mere ashes. The body of a Christian is a temple of the Holy Ghost, and though it is fated to see death, it will return again to life in glory. The cross, with which the ashes are traced upon us, is the sign of Christ’s victory over death. The words, “Remember, man, that thou art dust, and that to dust thou shalt return,” are not to be taken as the quasi-form of a kind of “sacrament of death” (as if such a thing were possible). It might be good stoicism to receive a mere reminder of our condemnation to die, but it is not Christianity. The declaration that the body must fall temporarily into dust is a challenge to spiritual combat, that our burial may be “in Christ” and that we may rise with him to “live unto God.”
Thomas Merton, Ash Wednesday, Spiritual Medicine