Question: Why did God send an angel as His representative to tell Mary that she would give birth to Christ?Sri Chinmoy: Because she had so much faith in angels. If I have faith in someone, then God will send that person to me because I will be more convinced that it is true. Then again, in this case, Joseph had more faith in angels than Mary had because he was simpler. Sometimes doubt was entering into Mary, whether the Saviour was actually coming. In the beginning Joseph wanted to discard Mary because it was not his child. Then an angel had to convince him that the child was destined to be the Saviour. After that his faith was stronger than Mary's.
Sri Chinmoy, Sri Chinmoy answers, part 25, Agni Press, 2000