It all began after the fall of man. God gave us a sign in genesis of the defeat of the serpent(satan) and sin. God said " i will put enmity between you(serpent) and the woman, between her seed and yours, you(serpent)will strike his heel, and he will crush you head".This is what we call the first gospel, the protoevangelium.
The “woman” in protoevangelium is not Eve because protoevangelium refers to future events and also the “seed” is singular whereas Eve has more than one seeds among them cain and abel.
Prophet isaiah again spoke of the sign…he said " a sign is given by the Lord, a Virgin(woman) shall give birth to a son, the son is called emmanuel meaning God with us"
Again isaiah said " a son is given to us(implying that there is a woman who gave birth), he is called prince of peace… mighty God…father…etc
The appointed time for the fulfillment of the sign comes.
An angel came to Mary and said "Hail daugther of zion, God has favored you. You will bear a son…Mary said “i know no man”. the angel said, the Holy Spirit will overshadow you… the son will be called the Son of God…And so… the Word was with God the Word was God the Word was made flesh and dwelt among us.
Indeed the Son of God is God with us(emmanuel) note: son of man is man, therefore Son of God is God at due time the Son of God choose to be born of a woman and became man therefore he is emmanuel.
Jesus confirmed that he is the “seed” while mary is the “woman”.why? jesus himself called his mother “woman” at the wedding in cana and also jesus called mary “woman” while jesus was on the cross.Jesus was therefore alluding to the “woman” in protoevangelium.
Here, the sign of the woman and her seed crushing the head of the serpent was definitely fulfilled at foot of the cross. Isaiah said(53:10) It is the Lord’s will that he(jesus) will suffer and his(jesus) death will bring forgiveness of sin. Jesus himself said speaking of his sacrificial death" drink this is my blood for the forgiveness of sin"therefore the death of Jesus was itself his crushing the head of the serpent.
From this we can say that those who oppose the sacrificial death of jesus or discredit it is contrary to the will of God(isaiah 53:10)
Lastly, revelation 12 speaks to us agin about a great sign,
Revelation 12 says…"a great sign appeared in the sky, a woman cloth with the sun with a moon under her feet and crowned with 12 stars. She is about to give birth.
a dragon also appeared in the sky ready to eat the son of the woman… but God protected the mother and the son.
the dragon(ancient serpent) was furious against the woman…The dragon made war against the sons of the woman those who believe in jesus."
(the last sentence tells us that those who belive in jesus are her sons too… this is the reason why we call Mary our Mother.)