The changes could have taken place before the final versions of Matthew and Luke. In this case the two evangelists would have been working from different versions of Q. It is simpler, however, to side with those scholars who argue that Luke deliberately introduced the changes. See, for example, Joseph A. Fitzmyer, The Gospel According to Luke (X-XXIV), Anchor Bible 28A (Garden City, NY: Doubleday, 1985), p. 913; and Heinz Schürmann, Das Lukasevangelium 2.1, Herders theologischer Kommentar zum Neuen Testament (Freiburg: Herder, 1994), p. 218.