"When Joseph awoke, he did what the angel had commanded him and took his wife with him." (Mt 1:24)
This phrase in the Gospel speaks volumes about the harmony between Joseph and Mary. The Fiat of Mary and the Fiat of Joseph are the fulfillment of the original harmony between Adam and Eve, the perfect resumption of the Sinai Covenant.
The Sinai Covenant was addressed to men and to women, something that the Jewish tradition stresses: "The Father of the universe proclaimed the ten words and oracles ... while the nation, men and women together, had gathered in assembly."(1)
At the beginning of the new Covenant, a man and a woman are called by God. Mary receives an announcement (Lk 1:26-38) and so does Joseph (Mt 1:18-25). After a short dialogue with the Angel, Mary gives her assent. Joseph first thinks of parting ways with Mary until the angel reveals to him the nature of his own mission.
Saint John Paul II wrote this about Mary on August 15, 1988:
"At the beginning of the New Covenant, which must be eternal and irrevocable, we find a woman: the Virgin of Nazareth."(2)
And this about Joseph, on August 15, 1989:
"The just man (Joseph), who carried with him all the heritage of the old covenant, was also made to enter the beginning of the new and everlasting covenant in Jesus Christ."(3)
Thanks to the "yes" of a woman (Mary) and the "yes" of a man (Joseph) God accomplished the New Covenant: the son of the Most High, the divine Word, took on our flesh to become, in the most sublime way, Emmanuel—God with us—and to be designated as the son of Mary (Mk 6:3) and the son of Joseph (Jn 1:45).
The Covenant made on Mount Sinai was like the birth of Israel as the people of God. It was as significant as the very genesis of the human race at the beginning of the world. At Sinai God created Israel to establish a pact of love. In the Garden of Eden, God created humanity (represented by Adam and Eve) for a pact of friendship.
But the sin of the golden calf, after Moses's ascent to Sinai, replicated the sin of Adam and Eve who disobeyed and in doing so destroyed the previously harmonious relationship with God.
Joseph and Mary are faithful to the Covenant: Joseph is just (Mt 1:19) and Mary is the humble servant of the Lord (Lk 1:48) and they fulfill the law of the Lord (Luke 2:23). Because of their union with God, Joseph and Mary truly lived as one person (Gn 2:24).
(1) Philo of Alexandria, De Decalogo, 32
(2) John Paul II, Apostolic Letter Mulieris Dignitatem (August 15, 1988), § 11
(3) John Paul II, Apostolic Exhortation Redemptoris Custos (August 15, 1989), § 32
Source: Marie de Nazareth Website