You've got it backwards.
The point is not that Jesus would become "unclean" or "contaminated" by sin.
The point is that sin can not exist where God dwells. They are incompatible. Where God is, sin is not. Sin can not abide the face of God and flees from it. God's dwelling place is the Holy of Holies, free from sin. There is no sin in heaven, for this very reason.
Therefore, regarding your point about the Holy Spirit in your other post, yes, the indwelling of the Holy Spirit within us helps us to overcome sin. To the extent that we allow God's grace given through the Holy Spirit to act in us, we will avoid sin. Sin will be driven out.
This theology applies to the womb of the Virgin Mary which was Jesus' dwelling for 9 months. Tradition and the teaching of the Church tells us that this dwelling place was likewise preserved pure and holy after Jesus' birth and forever after to underline the uniqueness of the Incarnation.
What explains the next thirty-three years?
Well, there sure seemed to be enough sin here on earth when Jesus walked it. The whole planet should have become sinless so Jesus could have walked it, but then He would not have been tempted in every way just as we are, nor would He have been crucified. Forgiveness is granted to those who ask it.
Besides, if sin cannot exist where God dwells, does that then mean that every believer who has the Holy Spirit living in him, as Jesus said He would, therefore sinless?
If we’re not sinless, then the Holy Spirit cannot live within us. It’s not a matter of helping us over come sin. If sin cannot exist where God dwells then that’s that. You can’t have it both ways.
And the Holy Spirit lives in believers for more than 9 months at a time. If Mary was sinless simply because she bore Jesus for only 9 months, what do you do with a person who has been a believer for years, or decades? Are they likewise sinless? Not becoming more sinless, but sinless, period, like Mary.
OTOH, if you do insist that since sin cannot dwell where God is, then that proves that once someone becomes a believer and has the indwelling presence of the Holy Spirit, that all their sins, past, present, and future ARE forgiven. God sees the believer that way, therefore can indwell him because that person has the righteousness of Christ imputed to him and positionally, in Christ, is indeed sin free, thus being sure of heaven.
If sinlessness is the result of being indwelt by God, then all believers are sinless.
Hasn’t that been labeled as some kind of heresy by the Catholic church?
It’s inconsistent to try to have it both ways.
The Incarnation was unique enough in its own right. It didn’t require that Mary remain sinless her entire life afterwards as *proof* of anything.
Jesus does not have a goddess mother.. His holiness exists independently of Mary..
Jesus came into the world to be fully human and fully divine.. he needed a human mother to have that be true..
Jesus ate with sinners.. drank with sinners and chose sinners to be His disciples .. remember He touched the woman with the issue of blood? That would have made Him "unclean"
It is commonly believed that original sin is passed from the Father not the mother.. as it was Adam that sinned ..even though Eve first tasted the apple.. ..
Because Jesus did not have a human father he was born without sin .. so he was fully human but without sin..