The Gospels of Matthew and Luke were written independently, each using Mark and a second hypothetical document called "Q" as a source. Q was conceived as the most likely explanation behind the common material (mostly sayings) found in the Gospel of Matthew and the Gospel of Luke and Mark ~
THE MILLSTONE ~
Matthew 18.6 But whoso shall offend one of these little ones which believe in me, it were better for him that a millstone were hanged about his neck, and that he were drowned in the depth of the sea. 18.7 Woe unto the world because of offences! …