What proof is there that Mary was born without sin?
Every person in the world is born without sin. Catholicism and most forms of Protestantism teach that Adam and Eve's fall brought sin into the world and that sin is passed down from generation to generation. This causes them a bit of difficulty. How do you explain the verses that say Jesus Christ had no sin? For Catholics, the answer is to state that Mary's birth was miraculous and that she was born without sin. Since Jesus was born of the Holy Spirit in Mary's womb, they can then say that no sin was passed on to Jesus. The major hole in this philosophy is that if Mary could be born without sin, then why not simply have Jesus born without sin and be done with it? If it required sinless parents, then wouldn't Mary's parents have to be sinless to produce a sinless daughter? Then what about their parents? Soon you will have worked your way back to Adam and Eve; and hence, everyone is born without sin. Protestants take a different approach (if they address the issue at all). They will say that the sin is passed down through men and since Jesus's father was God, he had no sin. The flaw here is that Luke 3:38 make the point that Jesus was a descendant of Adam. If sin is passed on to Adam's descendants, then Jesus would have to have the same; otherwise, you cannot claim that Jesus is a descendant of Adam.
The Bible teaches that sin comes from the actions of the person. "Behold, all souls are Mine; The soul of the father As well as the soul of the son is Mine; The soul who sins shall die" (Ezekiel 18:4). In particular, the Bible states that sin is not inherited. "The soul who sins shall die. The son shall not bear the guilt of the father, nor the father bear the guilt of the son. The righteousness of the righteous shall be upon himself, and the wickedness of the wicked shall be upon himself"(Ezekiel 18:20; see also Jeremiah 31:29-30). Punishment is based on what a person individually does or neglects to do. "But he who does wrong will be repaid for what he has done, and there is no partiality" (Colossians 3:25).
How do we explain the near-universal spread of sin in the world? Again, we can find the answer in our Bibles. "Therefore, just as through one man sin entered the world, and death through sin, and thus death spread to all men, because all sinned" (Romans 5:12). In the history of the world, we see the universal weakness of man in giving into sin. Paul lays out the proof in Romans 3 and sums it up thus, "for all have sinned and fall short of the glory of God" (Romans 3:23). Notice the active tense. It is not that we have all received sin from our parents, but that we have all committed sin in our lives. This would include Mary.
Jesus is the sole exception, which is one of the reasons He is uniquely qualified to be our Savior. "For we do not have a High Priest who cannot sympathize with our weaknesses, but was in all points tempted as we are, yet without sin" (Hebrews 4:15). Jesus alone lived a life untainted by personal sin. Thus He became the perfect, unblemished sacrifice for the sins of the world.