At the end of O. Henry's story, "The Gift of the Magi," he explains who the Magi were and how they are important to the story. He explains that the magi are the wise men who brought gifts to Baby Jesus in the Christmas Story. Each wise man brought something for Jesus (gold, frankincense and myrhh) so that they could worship Christ.
In the story of "The Gift of the Magi" both Della and Jim choose gifts that don't seem wise in the end, however, they both give up their most valued possessions. Despite the poor conditions they live in, Della and Jim are wealthy in love and generosity. O. Henry notes at the end that
"O all who give and receive gifts, such as they are wisest. Everywhere they are wisest. They are the magi."
This quote explains that Della and Jim's sacrifice is what makes them wise and "the magi" despite the seeming foolishness of their situation at the end. This story is often read as a story that showcases the true meaning of Christmas and giving.