Albert Barnes Commentary Matthew 15:24

"But he answered and said, I was not sent but unto the lost sheep of the house of Israel." — Matthew 15:24 (ASV)

But he answered—I am not sent, etc. This answer was made to the woman, not to the disciples. The lost sheep of the house of Israel were the Jews. He came first to them. He came as their expected Messiah. He came to preach the gospel himself to the Jews only. Afterwards it was preached to the Gentiles; but the ministry of Jesus was confined almost entirely to the Jews.