In the time of Jesus, people did not view children as especially innocent or pure. Instead, they saw them as weak and of low status. Jesus said that people should receive a child in his name (that is, as his representative).
Welcoming a child shows humility. It means choosing a low place and serving others (9:35; see also 10:13–16). Other teachings of Jesus show that how people receive or reject his followers is the same as how they receive or reject him (Matthew 10:40; 25:31–46; Luke 10:16; John 13:20).