The Coming of the Savior: Mary's Song, Why Sing?

The LORD is my portion; I promise to keep your words. I entreat your favor with all my heart; be gracious to me according to your promise. When I think on my ways, I turn my feet to your testimonies; I hasten and do not delay to keep your commandments. Though the cords of the wicked ensnare me, I do not forget your law. At midnight I rise to praise you, because of your righteous rules. I am a companion of all who fear you, of those who keep your precepts. The earth, O LORD, is full of your steadfast love; teach me your statutes!
                                                                                                                    - Psalm 119:57-64


46And Mary said, “My soul magnifies the Lord,47 and my spirit rejoices in God my Savior; 48 for he has looked on the humble estate of his servant. For behold, from now on all generations will call me blessed,49 for he who is mighty has done great things for me, and holy is his name.50 And his mercy is for those who fear him from generation to generation. 51 He has shown strength with his arm; he has scattered the proud in the thoughts of their hearts;52 he has brought down the mighty from their thrones and exalted those of humble estate;53 he has filled the hungry with good things, and the rich he has sent away empty. 54 He has helped his servant Israel, in remembrance of his mercy,55 as he spoke to our fathers, to Abraham and to his offspring forever.”
56 And Mary remained with her about three months and returned to her home.
                                                                                                                              - Luke 1:46-56