The first part of the 'Hail Mary' was spoken by the angel Gabriel just before Mary was invited to become the mother of Jesus. Her response was, "I am the handmaid of the Lord, let what you have said be done to me." By giving her life to God in this way, she became 'holy', and 'mother of God', and became a special intercessor who can 'pray for us sinners'.

Hail Mary, full of grace,
the Lord is with thee.
Blessed art thou among women,
and blessed is the fruit of thy womb, Jesus.
Holy Mary, mother of God,
Pray for us sinners,
Now, and at the hour of our death.