Passage Matthew 10:5–6
In Matthew 10:5-6 Jesus sends out the twelve and tells them not to go to the Gentiles or enter a Samaritan town, but to go to the lost sheep of the house of Israel. In Matthew 15:24-26 he tells the Canaanite woman who asks him to heal her daughter that he was sent only to the lost sheep of Israel, and that it is not right to take the children’s bread and throw it to the dogs.
The argument takes these sayings as plain evidence that his mission was to the Jews alone, which is hard to square with a message to all nations. (The New Testament text is not yet on this site.)
Source: see Credits and references (no. 21, p. 21).