My own preparation led me to compare and contrast Luke's telling of the story with Matthew's (3:7-10). Right from the beginning there is a significant difference from Matthew to Luke. Whereas John the Baptizer's message of repentance was aimed at the "Pharisees and Sadducees" in Matthew, in Luke the wilderness preacher's call is extended to "the crowds that came out to be baptized by him" (Lk 3:7). Matthew remembers that John called the "Pharisees and Sadducees" a "brood of vipers"; Luke remembers that John affixed that label to "the crowds". Regardless of audience, however, the purpose of John's preaching was the same: "Bear fruits worthy of repentance" (Lk 3:8; Mt 3:8).
Luke, for his part, spells out the exact nature of such fruit-bearing repentance. Luke's narrative will not allow "the crowds"--like the Pharisees and Sadducees--to ritualize repentance (water baptism being one such form) apart from the will to "turn around" or "change direction." Luke's John, more explicitly in this case than Matthew's, demands the making of amends. John's proclamation of repentance in Luke is the repentance of Genesis's Jacob, he who tried, with physical gifts, to return his father's blessing mischievously taken from Esau his brother (Esau, for his part, had the grace to forgive without need of restitution, though that in no way cancels Jacob's obligation, for his part, to give). Indeed, John's counsel to the crowds in Luke is,
"Whoever has two coasts must share with anyone who has none; and whoever has food must do likewise" (3:10-11).
It seems like a reasonable directive, one able to followed by rich and poor alike. "Whoever has two coats", John says, can give one to someone in greater need. "Whoever has food" should share with someone who has less (emphasis mine).
Advent, therefore, like the Christmas in which it ensues, is a time (and not the only time!) to put into practice the way of the kingdom which will arrive with the King, the one "coming after" John (see Lk 3:16). The preparation of Advent is the giving of gifts to others ahead of the Gift we all receive at Christmas.
-Joe