Jesus speaks pithy words here! Whenever one is thrown in the water with a millstone around his neck, that person will certainly drown. This punishment suits only the worst criminal. Apparently, Jesus takes it very seriously when his followers are tempted into stumbling. Whoever makes others stumble into sin does not deserve to live any longer. It is remarkable that Jesus describes his followers as these little ones.
This also shows how others may see them. Oh, these Christians mean nothing. They are the scum of society.
And yet, for Jesus, they are extremely precious. Another word of Jesus fits here: See that you do not despise one of these little ones. For I tell you that in heaven their angels always see the face of my Father who is in heaven
(Matthew 18:10; see also Psalm 34:7).
2 It would be better for him if a millstone were hung around his neck and he were cast into the sea than that he should cause one of these little ones to sin.