Well, if Mary’s blood had to be clean and pure so Jesus blood was clean and pure, how did Mary be born of a sinful mother? Would not Mary’s mother’s blood had to have been pure and clean so that Mary’s would have been, and so on back?
Now if God could do that kind of miracle for Mary so that she was born of a sinful mother sinless herself (presuming that to be the case), then why couldn’t God have done the same thing for Jesus that Catholics claim He did for Mary?
Do you understand where the sin nature comes from anyway?
That is the 'Immaculate Conception', as I understand it. I didn't know it for years, my assumption was that it was Jesus' birth. It wasn't, it was Mary's. That is this teaching - she was conceived without sin, so Jesus could be a perfect sacrifice.