In the Sermon on the Mount, Jesus addresses three aspects of the spiritual life—alms, prayer, and fasting—setting up his teaching on these topics with the assumption that his followers would indeed practice these disciplines. One can find many texts and traditions within Judaism that may provide the source for a trajectory to Jesus’ teaching, but that just pushes the question back one step: what gave rise to this teaching or tradition? Restricting the focus to fasting, various patristic writers have argued that fasting is intrinsic to the order of creation from its very beginning. The command of God to the first humans not to eat from the tree of the knowledge of good and evil is widely viewed as the source for the Christian practice of fasting. Failing to obey God’s commands to fast from eating the fruit of this tree, human beings essentially forsook their vocational mandate to function as priestly co-regents of God’s benevolence in the world (Gen 1:26-28; 2:15), disrupting the harmony of the triad of God/human beings/other-than-human creation. Here we see the ethical import of Jesus’ call to fast. Fasting recalls the original human vocational mandate to care for God’s creation. Its contextual connection to prayer and almsgiving in Jesus’ teaching highlights that fasting is both a spiritual discipline and an ethical act. As practiced in the Orthodox tradition, fasting connects with ecological concerns for the earth—is our consumption of meat, largely provided by mass production facilities, a faithful expression of our call to care for the earth? It also connects with economic justice—is, for example, corporate agriculture a just expression of social concern for poor workers or family farmers? Fasting becomes a spiritual practice not just by virtue of its ascetic character, but also due to its rather visceral ability to align human beings with the call to fulfill their vocational mandate to protect and serve the earth.