The angel tells Mary, “The Holy Spirit will overtake you.”
“An angel tells the young Mary that God has elected her to be the means whereby divine love will be enfleshed in the human world. As a parabolic character, Mary represents us. She is a normal human being, which means that she is, by nature as it were, self-centered, self-enclosed. So she asks, in effect: ‘How can that happen? I’m alone; it’s just me.’ The angel replies, ‘The Holy Spirit will overtake you, and the power of God will overshadow you…'”