The term "repentance" does carry the connotation of regret, but it means more than that. The Greek word metanoia that we translate as "repentance" means literally, "a change of mind." Not a simple "I'm sorry" or "I wish things could have been different," but rather a "I'm traveling a different way now."
Morna Hooker, in her commentary on Mark, lists the OT references implied in Mark's description of John: The rough garment of camel's hair is probably to be taken as an indication that he was a prophet (Zechariah 13:4). The reference to the leather belt echoes the description of Elijah (2 Kings 1:8). He calls the nation to repent as did Malachi (4:5). The locusts and honey are typical food for travelers in the wilderness and locusts were permitted in the Torah (Leviticus 11:21).
John is preparing his world for a new age with a new leader, one who is not only more powerful than the prophets who foretold his coming, but one who also is more powerful than the governors and Caesars of his time.
During this Advent season, let us remember John's promise. And let us remember that the Holy Spirit continues to work in the world and in our lives, to sustain us and to prompt us.
Lectio Divina: Mark 1:5-8; Psalm 85:8