“And Mary said: “My soul glorifies the Lord and my spirit rejoices in God my Savior, for the Mighty One has done great things for me— holy is his name.”
Luke 1:46-47, 49
Luke is the longest of the four gospels and the longest book in the New Testament; together with Acts of the Apostles it makes up a two-volume work from the same author, called Luke–Acts. The cornerstone of Luke–Acts' theology is "salvation history", the author's understanding that God's purpose is seen in the way he has acted, and will continue to act, in history. It divides the history of first century Christianity into three stages, with the gospel making up the first two of these – the arrival among men of Jesus the Messiah, from his birth to the beginning of his earthly mission in the meeting with John the Baptist followed by his earthly ministry, Passion, death and resurrection (concluding the gospel story per se).
Here, Christ's birth is going to have attendant blessings which Mary sings of, prior to the birth. There is debate about the writing having been revised over the years, as late as the second century. But there is only one interpretation to the words.