The feast of the baptism of Jesus is the second most ancient liturgical celebration and is among the major mysteries of Christ. The synoptics mention Jesus' baptism in the Jordan, and John's Gospel gives a report of it, indicating its importance. The Baptism of Jesus in the Jordan, a systematic study, isolates those themes (Trinitarian, cosmic, sinlessness, liturgical, messianic, divinization, orientation to a future paradise, descent into Sheol/hell, institution of the sacrament of baptism) with which the early Church proclaimed and celebrated the baptism of Jesus in the Jordan. Drawing on Latin, Greek, and Syrian sources, Father McDonnell shows the Jordan event as the dominant paradigm of Christian baptism in the earliest centuries, and also presents its relation to growing interest in the Pauline death and resurrection themes in the fourth century. Because it was widely looked upon as the institution of Christian baptism, this history is relevant to contemporary theology and to the liturgical celebration of Christian baptism. The way the early Church used the baptism of Jesus to communicate the central truths of the faith, especially proclaiming the call to holiness the vocation to participate in the divine life is still valuable today. Liturgists and systematic theologians teaching the sacraments will be particularly interested in this patristic, systematic work.