The father is completely unlike most fathers from the time period. Rather than being a strict upholder of discipline and the law, he forgives and embraces his wayward son, running out to meet him the as soon as he knows his son is on the road home. This was a different way to present God than Jesus's audience was used to. They expected powerful, harsh, and judgmental, not magnanimous and loving. Our God doesn't wait for our apology, but rushes out to meet us, embracing us and forgiving us unconditionally. He asks us to do the same.
This is the main message of this parable. Jesus was talking to the devoted religious of His time. He puts them in the place of the elder son who at first spurns the celebration out of anger for his father's generosity. While many of us easily see ourselves in the place of the younger son, the truth is that we often find ourselves in the role of the elder one. We need to learn it is not for us to sit in judgment of our fellow sinners. As our presider stated today, we need to look to our own faults more than the faults of others; if don't think we have faults, then we really need to be concerned.