How we cite our quotes: All quotations are from The Sound of Music.
Quote #1
REVEREND MOTHER: Maria, it seems to be the will of God that you leave us.
MARIA: Leave?
REVEREND MOTHER: Only for a while, Maria.
When the decision is made to send Maria to the von Trapp home, Reverend Mother attributes it to the will of God. (We assume she did a lot of praying about it before she came to that decision.) She knows that presenting it as God's will will make Maria take the plan seriously.
Quote #2
MARIA: "When the Lord closes a door, somewhere He opens a window."
Even though she's upset at being asked to leave the abbey, Maria tries to see God's role/presence in her new journey, just as the Reverend Mother suggested. For a devout person like her, this gives her confidence that things will work out, even though she's scared to death.
Quote #3
MARIA: God bless the captain. God bless Liesl and Friedrich. God bless Louisa, Brigitta, Marta and little Gretl. And oh, I've forgot the other boy—what's his name? Well, God bless what's-his-name.
Even though she's left the abbey, Maria's still devout. Praying by her bed on her first evening in the von Trapp house, she's careful to work the family into her prayers. Prior to leaving, she'd been afraid that would mean leaving her faith behind. Sounds like Maria's God has a sense of humor.