The Prodigal Son
The Prodigal Son is one of three parables told by Jesus in the Bible's Book of Luke. A man had two sons. The younger son asked for his inheritance upfront. The father gave it to him, and the son went to a far country and wasted his inheritance in riotous living.
Above, The Prodigal Son by Cornelis Cornelisz van Haarlem, 1638, shows the son at right surrounded by whores. We see a lot of female flesh in the painting, but there's also a nice naked musician at left.
The parable continues: after the son had spent all his money, there was a famine. The son was forced to become a swineherd, and he envied the pigs because at least they had something to eat while he was starving.
Above, The Prodigal Son, an inkstand by Urbino c. 1600 shows the son with a pig, but he looks too comfortable to me; he's supposed to be despairing.
The Prodigal Son by Emile Salome, 1863, above, show the son despairing.
The Prodigal Son by Rodin, 1905, also shows a despairing son.
Another view of Rodin's The Prodigal Son.
The parable continues: the son returns home to his father and says he has sinned. But the father rejoices, gives his son his best robe, and orders a feast with a fatted calf.
Above, The Prodigal Son by Kristian Zahrtmann, 1909.
This sculpture by George Grey Barnard c. 1904 also shows the return of the Prodigal Son to his father.
The parable continues: the older son is angry, saying that he had always behaved correctly, but the father never made a celebration for him and his friends like he was now doing for the younger son. The father answers that it is good to celebrate and be glad, because his brother was lost and now is found.
The moral of the story is supposed to be that God's love is boundless, and even if you sin, God will forgive you if you repent.
Above, a more modern work, a photo by Duane Michals, 1982, called Return of the Prodigal Son. Note that, like the artworks, the son is naked.
The Bible does not say that the son was naked. Why, then, do artists show the son naked? Perhaps because the son, having no money for food, would also have no money for clothes, and the fact that the father gave him a robe suggests that he needed one. But it seems more likely to me that the son would have been dressed in rags, not naked.
I think the main reason is that artists like to portray naked people. Note that in Barnard's sculpture, the father is naked, too.