Nowadays re-named the Solemnity of Mary, Mother of God, today is traditionally celebrated as the feast of the Circumcision of Our Lord. Both titles refer to the same concept, that is, that Jesus was born to a Jewish mother, the representative of the people of the Old Covenant, and that her son was full heir to the promises and obligations of that tradition. Only from that beginning could He inaugurate the New Covenant with all of mankind.
The Circumcision of Christ
Michael Pacher, 1430 - 1498
The St Wolfgang Altarpiece, 1479-81