This verse comes from the Song of the Three Holy Children (or the Song of Azariah), which is an addition to the Book of Daniel in the Old Testament (found in the Greek Septuagint and the Vulgate). It's a song of praise and adoration directed towards God while Shadrach, Meshach, and Abednego are in the fiery furnace.

Let's break down the verse:

"O you⌃ heavens, bless you⌃ the Lord...": This is a direct address to the heavens (the skies, the celestial realm). The phrase "bless you the Lord" (more accurately translated as "bless ye the Lord") is an imperative, meaning it's a command. The heavens are being called upon to praise, glorify, and acknowledge the greatness of God. It's an expression of encouragement and invitiation for the heavens to participate in the act of worshiping God.

"...praise and exalt him above all for ever.": This builds on the previous statement. It calls for continuous and unsurpassed worship. "Praise" means to express admiration and approval. "Exalt" means to elevate or lift up. To exalt God "above all" means to recognize his supreme authority and unparalleled glory, placing him above everything else in creation. This praise and exaltation should continue "for ever," signifying eternity.

In summary, the verse means:

The heavens are urged to acknowledge God's majesty, offer Him praise and adoration, and recognize His supreme and eternal nature. It is a call for all of creation to join in the never-ending worship of the Almighty. It emphasizes God's absolute sovereignty and the importance of giving Him ultimate honor.

Theological Significance:

This verse is important because it highlights the universality of worship. It is not only human beings who should praise God, but all of creation. It also underscores the importance of continuous and eternal praise. God is worthy of constant adoration because of His infinite greatness and eternal existence.