Here "this" refers to the question the Pharisees asked about Jesus eating with tax collectors and sinners.
# People who are strong in body do not need a physician, only those who are sick
Jesus answers with a proverb. He means that he eats with these kinds of people because he has come to help sinners. (See: [[rc://en/ta/man/translate/writing-proverbs]])
Jesus is using irony. He does not think there are any people who are righteous and do not need to repent. AT: "those who think they are righteous" (See: [[rc://en/ta/man/translate/figs-irony]])