This book proposes that Christian worship Is a key source for any theology seeking to understand the covenant between God and human beings in the Christian tradition. Through a detailed examination of phenomenological, biblical and theological sources, the author seeks to write a theology in which the selfhood of God and human beings is seen as essentially 'vowed' or 'covenantal'. This claim is then explored through a detailed examination of Eucharistic and baptismal practices within the worship life of the church. Here, then, is a theology that understands Christian worship as a mutual act of promising and commitment between God and human beings.