What does Luke 9:38 mean?

Jesus, Peter, James, and John are returning to the other disciples after Jesus' transfiguration (Luke 9:28–36). They arrive to find the nine arguing with scribes, surrounded by a crowd who quickly turn their focus from the argument to Jesus (Mark 9:14–15). We aren't told what the disciples and the scribes are arguing about. Presumably, it was related to this man's message. His only child has been demonized by an evil spirit that either gives him symptoms of epilepsy or exacerbates the disease he already has. Despite the fact Jesus has given the disciples the power to cast out all demons (Luke 9:1), they prove powerless, and the father begs for Jesus' help (Luke 9:39–40).

This is at least the third time Luke records Jesus coming to the rescue of an "only child." The first was the widow of Nain's son (Luke 7:11–15). The second was Jairus' daughter (Luke 8:41–42, 49–55). In that time and culture, being an "only child" was an important distinction. A significant part of the promise God gave the Jews refers to the perpetual ownership of the land. These parents need their children to inherit the family land and continue their family's position in the clan and the community. The widow especially needed Jesus' attention; without her son, she may have been destitute. If Jairus had no more children—and they still followed the Mosaic law—his daughter's husband would inherit his estate (Numbers 27:1–11). This father, too, both loves his son and needs him as an heir.