The evangelist Luke presents Mary in a unique way and this tradition is recounted by the council:
This union of the Mother with the Son in the work of salvation is made manifest from the time of Christ’s virginal conception up to His death it is shown first of all when Mary, arising in haste to go to visit Elizabeth, is greeted by her as blessed because of her belief in the promise of salvation and the precursor leaped with joy in the womb of his mother.(Cf. Lk. 1, 41-45.) This union is manifest also at the birth of Our Lord, who did not diminish His mother’s virginal integrity but sanctified it,(Cfr. Conc. Lateranense anni 649, Can. 3: Mansi 10, 1151. S. Leo M., Epist. ad Flav.: PL S4, 7S9. – Conc. Chalcedonense: Mansi 7, 462. – S. Ambrosius, De inst. virg.: PL 16, 320.) when the Mother of God joyfully showed her firstborn Son to the shepherds and Magi. When she presented Him to the Lord in the temple, making the offering of the poor, she heard Simeon foretelling at the same time that her Son would be a sign of contradiction and that a sword would pierce the mother’s soul, that out of many hearts thoughts might be revealed.(Cf. Lk. 2, 34-35) When the Child Jesus was lost and they had sought Him sorrowing, His parents found Him in the temple, taken up with the things that were His Father’s business; and they did not understand the word of their Son. His Mother indeed kept these things to be pondered over in her heart.(Cf. Lk. 2, 41-51.)
Union of Mother and Son: the Church’s artists have perhaps secured this image for us more profoundly than any other group, including theologians.