Why this level of detail?

Luke gives the appearance of John an exact dating with an elaborate chronology reminiscent of ancient historians like Thucydides and Josephus. Only the first phrase in verse 1 is necessary to fix the date, but Luke adds additional information—a rapid survey of the political situation at this crucial moment, a setting of the Christian gospel in its imperial and local history. With each detail Luke gives us about Tiberius, Pontius Pilate, Herod, and Philip, he is building the political, historical set for the opening scene of the adult John's ministry.

Why?

Because, like Mark, Luke views John's story as the beginning of Jesus' story, not the preview. The first two chapters of Luke are integral to the story. They aren't merely the twenty minutes of previews before the feature film begins. When, in 3:1-2, the narrator gives us more contextual detail than we think we need, it is because Luke believes that for us to understand Jesus we must understand John.

To be attentive to John's context may nudge us that we need to be attentive to our own. To prepare for the power of Jesus' message, we must not be naïve about the powers-that-be in our own context. Luke presents John in the mode of an Old Testament prophet who begins to preach in this region of the Jordan, summoning his hearers to an act of repentance leading to forgiveness of sin. His work is seen as the fulfillment of Isaiah 40:3-5 (Marshall, Commentary on Luke, 132).

In the Theater of Our Own Lives 

We each inhabit a particular scene or setting with particular historical, social, political, economic features. It is within that setting—not in some ethereal, spiritual, purely personal, inner realm—that we are called to repent and to prepare for the coming of Jesus Christ.

As I sit in the darkened theater watching the action in Luke 3:1-6, I don't see John sitting in his mother's kitchen waiting for things to start happening. I see him already out in the wilderness when God's word appears to him. A voice crying in the wilderness in the fifteenth year of the reign of Emperor Tiberius, when Pontius Pilate was governor of Judea, and Herod was ruler of Galilee, and his brother Philip ruler of the region of Ituraea and Trachonitis, and Lysanias ruler of Abilene, during the high priesthood of Anna and Caiaphas.

During Advent, Luke shows us John's stage set, and he challenges us to invite him into ours.

Sources Consulted

I. Howard Marshall, The New International Greek Testament Commentary on Luke (William B. Eerdmans Publishing Co., 1978).