“Mary, a Virgin not only undefiled but a Virgin whom grace has made inviolate, free of every stain of sin.”
– Saint Ambrose, Sermon 22:30 (A.D. 388).
“A virgin, innocent, spotless, free of all defect, untouched, unsullied, holy in soul and body, like a lily sprouting among thorns.”
– Saint Theodotus of Ancrya, Homily VI:11 (ante A.D. 446).
Luke 1:28 – also, the phrase “full of grace” is translated from the Greek word “kecharitomene.” This is a unique title given to Mary, and suggests a perfection of grace from a past event. Mary is not just “highly favored.” She has been perfected in grace by God. “Full of grace” is only used to describe one other person – Jesus Christ in John 1:14.
II. Mary – the Immaculate Ark of the New Covenant
Exodus 25:11-21 – the ark of the Old Covenant was made of the purest gold for God’s Word. Mary is the ark of the New Covenant and is the purest vessel for the Word of God made flesh.
2 Sam. 6:7 – the Ark is so holy and pure that when Uzzah touched it, the Lord slew him. This shows us that the Ark is undefiled. Mary the Ark of the New Covenant is even more immaculate and undefiled, spared by God from original sin so that she could bear His eternal Word in her womb.
1 Chron. 13:9-10 – this is another account of Uzzah and the Ark. For God to dwell within Mary the Ark, Mary had to be conceived without sin. For Protestants to argue otherwise would be to say that God would let the finger of Satan touch His Son made flesh. This is incomprehensible.
IX. Misunderstanding about Romans 3:23 (“All have sinned”)
Rom. 3:23 – Some Protestants use this verse “all have sinned” in an attempt to prove that Mary was also with sin. But “all have sinned ” only means that all are subject to original sin. Mary was spared from original sin by God, not herself. The popular analogy is God let us fall in the mud puddle, and cleaned us up afterward through baptism. In Mary’s case, God did not let her enter the mud puddle.
Rom. 3:23 – “all have sinned” also refers only to those able to commit sin. This is not everyone. For example, infants, the retarded, and the senile cannot sin.
"Now to Him who is able to keep you from falling and to present you without blemish before the presence of His glory with rejoicing, to the only God, our Savior through Jesus Christ our Lord, be glory, majesty, dominion, and authority, before all time and now and for ever." (Jude 24-25)
Source: https://www.scripturecatholic.com/blessed-virgin-mary
