There is such a simple, yet awe inspiring distinction between Hannah's praise to God when presenting Samuel in the temple...
1 Samuel, ch. 2
1: Hannah also prayed and said, "My heart exults in the LORD; my strength is exalted in the LORD. My mouth derides my enemies, because I rejoice in thy salvation.
2: "There is none holy like the LORD, there is none besides thee; there is no rock like our God.
3: Talk no more so very proudly, let not arrogance come from your mouth; for the LORD is a God of knowledge, and by him actions are weighed.
4: The bows of the mighty are broken, but the feeble gird on strength.
5: Those who were full have hired themselves out for bread, but those who were hungry have ceased to hunger. The barren has borne seven, but she who has many children is forlorn.
6: The LORD kills and brings to life; he brings down to Sheol and raises up.
7: The LORD makes poor and makes rich; he brings low, he also exalts.
8: He raises up the poor from the dust; he lifts the needy from the ash heap, to make them sit with princes and inherit a seat of honor. For the pillars of the earth are the LORD'S, and on them he has set the world.
9: "He will guard the feet of his faithful ones; but the wicked shall be cut off in darkness; for not by might shall a man prevail.
10: The adversaries of the LORD shall be broken to pieces; against them he will thunder in heaven. The LORD will judge the ends of the earth; he will give strength to his king, and exalt the power of his anointed."
...and the Magnificat...
46: And Mary said, "My soul magnifies the Lord,
47: and my spirit rejoices in God my Savior,
48: for he has regarded the low estate of his handmaiden. For behold, henceforth 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 on those who fear him from generation to generation.
51: He has shown strength with his arm, he has scattered the proud in the imagination of their hearts,
52: he has put down the mighty from their thrones, and exalted those of low degree;
53: he has filled the hungry with good things, and the rich he has sent empty away.
54: He has helped his servant Israel, in remembrance of his mercy,
55: as he spoke to our fathers, to Abraham and to his posterity for ever."
The covenant promises are all in past and past perfect tense. Mary is declaring that the covenant Hannah praises in the OT has been fulfilled by the Incarnation. Considering Christ was in-utero when she proclaimed this, these are words of immense power and faith!
Mary, conceived without sin, pray for us who have recourse to thee.