When I issued my "lament for unanswered questions" last month, I had just read Jeremiah 31:34--"for I will forgive their iniquity, and remember their sin no more"--and was reminded that for several years now I've wanted to think about what it would have meant for Jesus to forgive sins in a first century context. The question is somewhat embarrassing since forgiveness is so prominent in the Gospels, and because I used to think forgiveness of sins was the main thing about being a Christian. It doesn't help that most of my first year students assume that the meaning of passages like Luke 5:20 and 7:48 is obviously to show that Jesus is God. (Why couldn't the Pharisees understand?) To be sure, Luke's Christology is high indeed, and the passages emphasize the son of man's authority to forgive sins; Jesus acts on God's behalf.
My question, though, is not with Christology, but with why Jesus would forgive sins in the first place when there was a functioning cult center in Jerusalem that operated a system of atonement that had been established by God. Why forgive sins when this is what the Temple was for?
(1) E.P. Sanders, who has probably done more than anyone else to raise the question, concluded that the historical Jesus offered forgiveness without requiring repentance from the sinners he gathered around him. Unfortunately, Sanders does not help us with Luke's understanding of forgiveness because Luke is careful to emphasize that Jesus called sinners "to repentance" (5:32).
(2) John Howard Yoder connected the forgiveness of sins to Jesus' quotation from Isaiah 61 in Luke 4:18, and argued from allusions in Isaiah 61 to the year of Jubilee (Lev 25) that Jesus meant to inaugurate God's Jubilee. Announcing forgiveness is the Jubilee 'release' in action. See this post for more details on Jubilee imagery in the OT.
(3) N.T. Wright argues that Jesus believed the Temple's system of atonement was broken, and that forgiveness in Jesus' ministry means what it did in Jeremiah: return from exile. It's an interesting suggestion with a great deal of explanatory power when it comes to the New Testament, but--as I've suggested elsewhere--the idea that most Jews believed they were in exile is problematic.
Although I have been working around the question for a little while, I have not yet taken the time to work carefully through the theme of forgiveness in Luke-Acts, and I'm still puzzled. If you can point me to the answer, please do so!