In our present age in which apostolic Christianity is a foreign notion to many Christians, it is of little wonder that many of the beliefs of our ancient fathers have been deemed outdated, including the importance of fasting. By exploring the Holy Scriptures, patristics, Christian tradition, and personal experience, Lutheran seminary professor Harold Ristau seeks to answer the question ""Why fast?"" Through this concise examination of a historic Christian practice, which is as rich with meaning today as it was in antiquity, the reader is left with a deepened appreciation for Christian fasting. Ristau's lively reflections on the relevance of fasting for catechesis, evangelism, and spiritual warfare fill the soul with great consolation. After all, our Lord Jesus' words--""when you fast""--presume that this vital discipline is already happening, and perhaps without you even knowing it. ""If you've ever wondered about the whys and wherefores of fasting, this is the book for you. Harold Ristau thoroughly explores Luther's well-founded objections to abuses of fasting in the medieval church. Yet he probes deeper, initiating contemporary readers into the evangelical/sacramental mysteries of fasting as practiced by the ancient church and taught by Jesus. In an age bloated with extravagance, Ristau invites Christians to discover firsthand that less is truly more: when we feast on Christ's fasting we experience the blessings of those who hunger and thirst for his righteousness."" --Harold L. Senkbeil, Executive Director, DOXOLOGY: The Lutheran Center for Spiritual Care and Counsel ""Dr. Ristau's book delves into the seldom-discussed practice of Christian fasting. This approachable work allows the reader to reflect on how this ancient practice might be incorporated into his or her devotional life."" --Thomas Korcok, Associate Professor of Theology, Concordia University Chicago, Director of the Center for Advancement of Classical Lutheran Liberal Arts ""In an age of abundance and amusement, Rev. Dr. Ristau's insights on fasting inform Christians seeking to authentically live a countercultural and graceful life. This engaging book offers an overview of fasting in Scripture and in Christian history and thought, and focuses on fasting as a satisfying gift of God. When You Fast relevantly shows that fasting is Gospel living in, with, and under the fullness of God's grace."" --Joshua Hollmann, Associate Professor of Theology, Concordia College New York Harold Ristau, Lutheran pastor and retired military chaplain, is an associate professor at Concordia Lutheran Theological Seminary in St. Catharines in Ontario, Canada. He is the author of several books, the two most recent of which are: My First Exorcism: What the Devil Taught a Lutheran Pastor about Counter-cultural Spirituality (2015) and At Peace with War: A Chaplain's Meditations from Afghanistan (2012).