What does Luke 15:15 mean?
The prodigal—wastefully spending (Luke 15:13)—son took the inheritance meant to build his family and fled to a foreign land. The money went to various obscene pleasures (Luke 15:30) which provided no joy and no lasting future. Shortly after he realizes his money is gone, a severe famine descends upon his new home. Instead of paying to experience pleasure, he's reduced to menial labor in the hopes of earning enough to survive (Luke 15:11–14).The son replaced the yoke that was easy and light (Matthew 11:30) for the boot of an oppressor. Like all of us, at times, he is seduced by the mirage of freedom which surrounds sin. Sin tempts us to become a slave to those who use us, rather than remaining children of a loving father, because it deceptively feels "freer" (Romans 6:16; James 1:14–18).
Pigs are not as unsanitary as portrayed in popular culture. However, they love rolling in mud, will eat almost anything, and their dung is arguably the most foul-smelling of typical barnyard animals. Worse, for the young man in this parable, they are ceremonially unclean for a Jew. The son of a wealthy Jewish landowner finds himself feeding animals his culture finds repulsive. Even worse, he grows to be jealous of despised swine: wishing he were one of them because at least then he'd get food (Luke 15:16).
Pharisees have criticized Jesus for associating with sinners and tax collectors (Luke 15:1–2). They see Jesus' friends much like the younger son: Jews who have rejected the dignified title of God's chosen people for the transitory and unclean "blessings" of the world. Jesus sees the sinners as lost. Like the older brother, the Pharisees follow the letter of the law, but they do not know their Father's heart. They don't understand their Father is inviting them to join Him in celebration when the lost are found and the spiritually dead find life (Luke 15:31–32).