Second Council of Constantinople, Capitulum VI

If anyone shall not call in a true acceptation, but only in a false acceptation, the holy, glorious, and ever-virgin Mary, the Mother of God, or shall call her so only in a relative sense, believing that she bare only a simple man and that God the word was not incarnate of her, but that the incarnation of God the Word resulted only from the fact that he united himself to that man who was born [of her];^[309] if he shall calumniate the Holy Synod of Chalcedon as though it had asserted the Virgin to be Mother of God according to the impious sense of Theodore; or if anyone shall call her the mother of a man (ἀνθρωποτόκον) or the Mother of Christ (Χριστοτόκον), as if Christ were not God, and shall not confess that she is exactly and truly the Mother of God, because that God the Word who before all ages was begotten of the Father was in these last days made flesh and born of her, and if anyone shall not confess that in this sense the holy Synod of Chalcedon acknowledged her to be the Mother of God:  let him be anathema.

Source edition notes

[309] The text here is uncertain, and the Latin and Greek do not agree.  Vide Hefele.

Translation: Henry R. Percival, The Seven Ecumenical Councils, NPNF II.14 (1900), via CCEL.