I have been converted to OSAS by your ministry. However, I must disagree with your use of the parable of the prodigal as proof of the OSAS doctrine. That is the story of the licentious son and the legalistic son, neither had a relationship with their father, as one was in a far country and the other was in a far field. The only way a person can be saved is through repentance and before the prodigal repents, he is merely a lost youth trying to find fulfillment in life.
First, let’s review the meaning of repentance to make sure we’re on the same page. The Greek word translated “repent” in the Bible is “metanoeo”. It means to change our mind about something. It’s a combination of “meta” (after) and “noeo” (to perceive or understand). It’s like saying, “I used to believe one way, but that was before I understood. Now that I understand I believe a different way. I have repented.”
But the importance of the parable as it concerns OSAS is that even when he was away living his life of sin, the prodigal never stopped being his father’s son. It’s an argument against the notion that believers can walk away from their connection to God. When we are born again we literally become one of God’s children (John 1:12-13). At that time God adopts us into His family in the same sense that an earthly father adopts a child. It’s a legally binding transaction that cannot be reversed and gives us the full right of “sonship”. This is proven by Paul’s statement that we are not only His children but also His heirs (Galatians 4:4-7). Only children with legal standing can be heirs to their father’s estate.
The prodigal went through a period of rebellion and left his father’s house but there was nothing he could do to sever his connection to his father. He could not stop being his father’s son. Once we are born again the same restriction applies to us. In 2 Cor. 1:21-22 Paul wrote that God has set his seal of ownership on us and put His spirit in our hearts as a deposit guaranteeing this.