Luke 15:1-2, 11-12
Kenneth S. Wuest Translation
1-2 Now, all the tax collectors and those sinners stained with certain vices and crimes were continually crowding close to Him for the purpose of hearing Him. And the Pharisees and those learned in the sacred scriptures went to grumbling in a low undertone muttering, conferring secretly with one another and discontentedly complaining, saying, This fellow is giving sinners access to himself and his companionship and is eating with them. And He (the Lord Jesus) gave them this illustration, saying...
11-12 And He said, A certain man has two sons. And the younger of them said to the father, Father, give me directly the share of the estate which falls to me.
Man = human (earthly father)
younger one = represents the tax collectors (sinners)
older one = represents the Pharisees and Sadducees
The earthly father, who is saved, has two unsaved sons. One of them, the younger one who later became saved (verse 32 "was dead and is alive"), went away but came back home after spending all his money. Because the text of verse 11 says, "a certain man has two sons," we strongly suggest that this father does not represent God. Instead, it represents a human being. And this man is a saved person because of verse 32, "Now, to make merry and to rejoice was a necessity in the nature of the case, because this brother of yours was dead and is alive, and has been lost and has been found." Only a believer can say such a statement.
Contrast this to the elder son who was extremely angry (verse 28) "but he flew into a rage that was the explosive outlet of a long time resentment against his brother, a resentment that had been smouldering in his breast" (like Cain and Abel hatred). And when the elder son responded to his father, he tried to justify himself as being righteous, which reflects the Pharisees' attitude. "And answering he said to his father, Look. So many years I am slaving (under law) for you, and never did I neglect your order. And to me you have never given even a young goat in order that with my friends I might make merry. But when this son of yours, the one who went through your money with harlots (refer to verse 2), came, you slaughtered for him the fatted calf," verses 29-30.
The key verse of the illustration of the prodigal son is verse 1 and 2. Always keep in mind when reading the prodigal son, the first and second verses of chapter 15. The Lord Jesus was pointing to the attitude of the Pharisees, who are self-righteous and who think they don't need repentance, through this illustration.
It would be a bad interpretation to say the "father" in this text is God, because this text is addressed to the Jews, and Jews never call God their "father". Also, if this "father" refers to God, this means the elder son and the younger son are both saved, and the younger son would be a backslidden Christian. But if he is a backslidden Christian, the Lord Jesus would not use the phrase "dead and is alive." Likewise, if we say that the two sons were saved, this would go against verses 1 & 2 of the context wherein the Lord Jesus pointed at the Pharisees and Sadducees who were murmuring against Him disrespectfully, thinking that He was doing the wrong thing by eating with sinners.