“Let it be done.” Mary’s “yes” to God is her Fiat. It is her complete obedience to God, allowing His will to be done in her life.
Handmaid
:
The personal servant of the head of a household who would do all that her master asked of her. When Mary told the Angel Gabriel that she was the handmaid of the Lord, she was saying that she was the servant of God, ready and willing to do all that He would ask of her.