The story is found in Luke 15:11-32. Jesus tells the story of a man who has two sons. The younger demands his share of his inheritance while his father is still living, and goes off to a distantcountry where he "waste[s] his substance with riotous living", and eventually has to take work as a swine herder (clearly a low point, as swine are not kosher in Judaism). There he comes to his senses, and decides to return home and throw himself on his father's mercy, thinking that even if his father does disown him, that being one of his servants is still far better than feeding pigs. But when he returns home, his father greets him with open arms, and hardly gives him a chance to express his repentance; he kills a fatted calf to celebrate his return. The older brother becomes jealous at the favored treatment of his faithless brother and upset at the lack of reward for his own faithfulness. But the father responds "Son, thou art ever with me, and all that I have is thine. It was meet that we should make merry, and be glad: for this thy brother was dead, and is alive again; and was lost, and is found".
The story has famously been covered in many forms of modern media including songs such as Billy Idol - Prodigal Blues, U2 - The First Time, Iron Maiden - Prodigal Son and films such as We Own The Night.