Luke 2:21

When eight days were accomplished— Among the Jews it was reckoned dishonourableto keep company with persons uncircumcised: Acts 11:3 wherefore, to render Jesus acceptable to the Jews, to fit him for conversing familiarly with them, and to qualify him for discharging the other duties of his ministry, it was in some sense necessary that he should be circumcised. Besides, as the Messiah was to be the descendant of Abraham, whose posterity was distinguished from the rest of mankind by this rite, he received the seal of circumcision, to shew that he was rightly descended from that patriarch. And further it was necessary that Jesus should be circumcised, because thereby he was subjected to the law of Moses, and put into a condition to fulfil all righteousness.