What does Luke 1:53 mean?

In psalms, prophecies, and other forms of praise, Scripture often speaks of God's impending acts as if they have already happened. Since God's promise is absolute, that which He declares is "as good as done." As Mary (Luke 1:26–27) rejoices over her role in the birth of Jesus Christ (Luke 1:31–33), she is making many allusions to the Old Testament (Luke 1:46–52). Many of these serve a dual purpose. They praise God for what He has already done, as well as celebrating how the Messiah will accomplish these things in an ultimate, final way (Isaiah 9:6–7; Revelation 19:11–15; 21:1–5).

Prior verses noted God's power and holiness being expressed in humiliating the arrogant, while uplifting those rejected by the world (Daniel 4:37; Psalm 89:13; Obadiah 1:4; Isaiah 13:11; 1 Samuel 2:8). Here, Mary makes another contrast. God's work sustains those who are needy (Psalm 34:10; Matthew 6:31–33). At the same time, He demonstrates that earthly wealth has no eternal value (Luke 6:24).