Verse 1 Tiberius reigned from ad 14-37 and the fifteenth year would, in principle, be ad 28-29. This is the clearest dating of the ministry of John and therefore of that of Jesus, as far as it goes. Things are not quite as crisp as that because Tiberias had three years co-regency before the death of Augustus and, in any case, different calendars were in use (Julian, Jewish, Syrian-Macedonian, and Egyptian).
A complicating factor is the fact that the first three Gospels portray a ministry of one year while John’s gospel has a three-year ministry. John’s time span is much more plausible. Pilate was prefect of Judea from ad 26 to 36.
Tetrarch meant a ruler of one fourth of a region, reflecting the division of the territory of Herod the Great after his death. Herod Antipas ruled in Galilee (4 bc - ad 39) and his brother Philip was Tetrach of Ituraea and Trachonitis (4 bc - ad 34). Nothing whatsoever is known of Lysanias who ruled in Abilene, north of Galilee, in the anti-Lebanon mountain range. Why Luke would mention Lysanias at all is an enigma to scholars.
Verse 2 Annas served as high priest from ad 6 to 15, and was succeeded by his son-in-law, Caiaphas, who served from ad 18 to 36. Technically, there was only one high priest as any one time, but people regarded Annas as still high priest even if “emeritus.”
Finally, the important expression is heard: “the word of God came to X”, used with arresting frequency to introduce a man of God in the Old Testament (110 times in all, with Jeremiah as most representative—Jer 1:2, 4, 11, 13; 2:1; 13:3, 8; 16:1; 18:5; 24:4; 28:12; 29:30; 32:6, 26; 33:1, 19, 23; 34:12; 35:12; 36:27; 37:6; 39:15; 42:7; 43:8). The evocation of Old Testament models is very effective. The wilderness is both literal and symbolic. As symbol, it recalls the place of Israel’s formation as God’s covenant people.
Verse 3 Four key terms are used: proclaiming, baptism, conversion (metanoia) and forgiveness. “Proclaiming” means literally heralding (hence our word kerygma). The baptism of John was a prophetic gesture, involving a once-off immersion, to be distinguished from the later baptism of Christian tradition.
As usual, “repentance” is not adequate here because it denotes only regret for the past whereas metanoia points to a turning around, so as to get a radically new view and direction forwards. In part, the turning around involves a change of behaviour, in response to forgiveness. Metanoia (as a verb) recurs only a few times in Luke: Luke 3:8; 5:32; 15:7. However, it comes back resoundingly at the end of the Gospel in Luke 24:45–47. There is a somewhat wider use in the Acts of the Apostles (Acts 5:31; 11:18; 13:24; 19:4; 20:21; 26:20).
Verses 4-5 Luke has extended considerably the citation first found in Mark 1:2. By the adjustment of punctuation (noted above), the text is made to point to John the Baptist, who was the voice crying out in the wilderness.
Verse 6 The last line is adjusted to “all flesh shall see the salvation of God”, echoing Is 51:10 and 2 Esd 6:25, as was seen above. Thus, Luke universalises even the ministry of John the Baptist, as a preparation for the proclamation of Jesus. Salvation (as noun and verb) recurs: Luke 1:47, 69, 71, 77; 2:11, 30; 3:6; 19:9; Acts 4:12; 5:31; 7:25; 13:23, 26, 47; 16:17; 27:34; 28:28.