Dear Leon:

It comes from the logic of the Marian Dogmas. Mary is the Immaculate Daughter of the Heavenly Father, she is the Ever-Virgin Spouse of the Holy Spirit, and she is the Blessed Mother of the Only-Begotten Son.

The Biblical basis of this notion comes from Saint Luke Chapter One in the account of the Annunciation where St. Gabriel the Archangel announces the how she will bare a child. He says that it is by the power of the Holy Spirit who will overshadow her.

Marriage is a mystical union created by God, not by man. It is only within marriage that man and woman become "one flesh." This does not mean intercourse, but a mystical and spiritual "one flesh" or unity. God is one, God is unity, and this state that creates a family is one of unity created by God, in His image. God Himself is family—Father, Son, and Holy Spirit. Thus, sex and procreation outside of this economy is evil.

God, who is consistent and holy in all things, does not do anything outside of this economy that He himself created. Mary was mystically and spiritually wed to God the Holy Spirit. If she was not then the Holy Spirit would have committed a spiritual fornication. That is not possible.

Mary is God's daughter, as we all are His sons and daughters. Mary is the mother of Jesus, the Only-Begotten Son, the Second Person of the Holy Trinity, God, as is stated in Scripture when Elizabeth said in Luke 1:43, "And why has this happened to me, that the mother of my Lord comes to me?"

That Mary was mystically and spiritually married is also one of the reasons that Mary was Perpetually Virgin. If Mary had sex with Joseph after the birth of Jesus, she would have committed adultery.

We see a similar mystical and spiritual marriage with God in the Religious life. Nuns actually wear wedding rings. Brothers are also wed to God. If Religious were to have sex with someone, they are not committing fornication as a single person, but adultery as a married person.

Our Blessed Mother is the beautiful, perfect, and holy model of family. She is daughter, spouse, and mother.

God Bless,
Bro. Ignatius Mary