The perpetual virginity of Mary is one of the four Marian dogmas of the Catholic Church, and states that Mary, the mother of Jesus, was a virgin ante partum, in partu, et post partumbefore, during and after the birth of Christ.

Then he brought me back to the outer gate of the sanctuary, which faces east;
and it was shut. And he said to me, “This gate shall remain shut; it shall not be
opened, and no one shall enter by it; for the Lord, the God of Israel, has entered by
it; therefore, it shall remain shut.”
Ezekiel 44, 1-3

A garden enclosed is my sister, my spouse;
a spring dried up, a fountain sealed.
Song of Solomon 4, 12

Behold thou shalt conceive in thy womb, and shalt bring forth a son; and thou shalt call his name Jesus. He shall be great, and shall be called the Son of the Highest; and the Lord God shall give unto him the throne of David his father; and he shall reign in the house of Jacob for ever. And of his kingdom there shall be no end. And Mary said to the angel: How shall this be done, because I know not man? And the angel answering, said to her: The Holy Ghost shall come upon thee, and the power of the Most High shall overshadow thee. And, therefore, also the Holy which shall be born of thee shall be called the Son of God.
Luke 1, 31-35

Therefore, the Lord himself shall give you a sign.
Behold the virgin shall conceive, and bear a son,
and his name shall be called Emmanuel.
Isaiah 7, 14

Before she was in labor she gave birth;
before her pain came upon her she was delivered of a son.
Who ever heard of such a thing, or who ever saw the like?
Can a land be brought forth in one day,
or a nation be born in a single moment?
Yet Zion was scarcely in labor when she bore her children.
Shall I bring a mother to the point of birth,
and yet not let her child be born? says the LORD.
Or shall I who bring to birth yet close her womb?
says your God.
Isaiah 66, 7-9

And Joseph also went up from Galilee, from the city of Nazareth, to Judea, to the
city of David, which is called Bethlehem, because he was of the house and lineage of
David, to be enrolled with Mary, his betrothed, who was with child. And while the were there,
the time came for her to be delivered. And she gave birth to her first born son and wrapped him
in swaddling cloths, and laid him in a manger, because there was no place for them in the inn.

Luke 2, 4-7

And the angel of the Lord appeared to him
in a flame of fire out of the midst of a bush;
and he looked, and lo, the bush was burning,
yet it was not consumed.
Exodus 3, 2

I will declare the decree:
the LORD hath said unto me,
Thou art my Son;
this day have I begotten thee.
Psalm 2, 7

Salve Regina