Mark 9:42

And whosoever shall cause one of these little ones that believe on me to stumble, it were better for him if a great millstone were hanged about his neck, and he were cast into the sea.

In this whole paragraph, and especially beginning here, there are a number of maxims in which no clearly discernible connective theme exists. They are isolated sayings of the type that Jesus uttered frequently and in various contexts, and they seem to have been written down here in the order of Mark's remembrance of them. See under Mark 9:1.

The teaching of this verse regards the extreme gravity of causing any humble believer to lose his faith in the Lord. Persons guilty of such a breach of the will of God would be better off drowned in the sea. The word for "millstone" here means "a millstone drawn by an ass," that is, a very large one, and contrasting with the smaller "hand millstone."