His father embraces him. Then, the son speaks his words of repentance.
Or, paying attention to the introductory words of this chapter about the grumbling Pharisees and scribes, I can read this parable metaphorically. Who is welcome at the table? What prevents someone from being worthy of sharing a meal with us? Who gets to decide? Which comes first--repentance or grace?
Further, what is this grace for, anyway--and, who's it for? Remember that Abraham was blessed to be a blessing (Genesis 12:1-3. Remember Jonah's assignment. (Thanks to Allen & Williamson, once again). Also, remember that foreigners had been included in the Exodus (Numbers 9:14; Judges 1:16)