All of us are born with sin in us because of the original sin of Adam and Eve. This original sin is removed when we are baptized. According to Sacred Tradition, the only created human conceived without original sin is Mother Mary. She was given this grace because she was being prepared to become the Mother of Jesus. So Angel Gabriel announced to Mary: 'Hail, Mary, full of grace! The Lord is with you!'. She was sinless from the moment she was conceived. This is known as the Immaculate Conception. This great feast is celebrated on 8 December.