In the same way, it is not the will of your Father in heaven that one of these little ones perish. Matthew 18:14
Jesus has been addressing the disciples about their question on who is the greatest in the kingdom of heaven. As Jesus has been outlining the needed humility, dependence, and holiness of his followers, there is also a sense that being great in the kingdom is related with the lives of others who are following Jesus. These are the "little ones" that Jesus repeatedly refers to in Matthew 18.
In this week's text, Jesus invites the disciples to enter into the heart of our Father in heaven in regard to those followers of Jesus who are struggling and wandering in their faith.