In the beautiful short story "The Gift of the Magi" by O. Henry, sacrificial love is the main theme, and the author develops it masterfully. First, he introduces the couple Jim and Della Young. He makes it clear that they are very poor and that they have to scrape for every penny. Their couch is shabby, their furnishings are sparse, Jim's salary is small, and they live in a cheap apartment.
However, the author also makes it clear that Jim and Della love each other very much. Despite their poverty, they are happy, because they have each other. Della is heartbroken that she cannot buy Jim a Christmas present that suitably expresses her love, and later, we find out that Jim feels the same way.
O. Henry then lets readers know that Jim and Della each have one possession that they value above all others. For Jim, it is a gold watch, a family heirloom that had previously been his father's and grandfather's. For Della, it is her long, shiny, luxuriant hair.
We see, then, that the author has beautifully developed the text to set up the situation. Della and Jim are poor, they want to express their love to each other through an impressive Christmas present, and they each have one thing that they consider valuable.
We are ready now for one of O. Henry's famous surprise endings. To show her love, Della sacrifices the beautiful hair that she values so much so that she can buy an expensive fob for Jim's watch. At the same time, to show his love, Jim sells the valuable watch that has been in his family for generations so that he can buy Della some expensive combs to go in her hair. Each one's sacrifice has negated the value of the other's gift.
We can see, though, that in the end it is not the gifts that are so valuable. The real value is in the sacrificial love that prompted the gift-giving.