The words from Scripture that are spoken as the ashes are applied to the forehead are "Dust you are and to dust you will return." God created man from the dust and woman from the man. We are living beings because God has breathed life into us and we are God's children because we received God's Spirit in the washing of Holy Baptism. Jesus has redeemed us from sin and death on the cross and calls us to lives of holiness. Our bodies are temples of the Holy Spirit. Although we struggle with sin, we live the new life we are given in Christ with hope of the life to come. God's salvation includes both body and soul. The Christian life is concerned with both body and soul. Forgiveness is needed so that we are washed on the inside. When we are cleansed on the inside this affects how we treat ourselves and our neighbor. Sin produces selfish desires. Christ calls us to live outside of ourselves, not seeking our wants and desires, but first to seek God's face in Christ and seek the welfare of our neighbor. This does not mean that we are to totally neglect ourselves. Rather we are to deny ourselves and discipline ourselves that we grow to be like Christ. To be like Christ is not possible without being "in Christ." This is where Holy Baptism comes in and the ongoing life of hearing God's Word and partaking of His Body and Blood at the altar. He feeds both body and soul. Just as He rose from the dead so He prepares us for the resurrection of our own bodies and the life eternal. So the ashes are not given to remind us that we will becomes ashes. They are given to remind us of the cross of Christ that we bear in this life and through which we are redeemed and given eternal life. The words from Scripture remind us that we will return to dust but for only for a while.
(excerpt from the Ash Thursday homily)