The answer is: Thousands upon thousands of angels

Rev 5 vs 11-12

In the grand symphony of the Book of Revelation, this declaration, often sung by multitudes of angels, carries profound significance that echoes throughout the entire biblical narrative. The "Lamb" is, of course, a powerful metaphor for Jesus, evoking the imagery from the Passover lamb in Exodus, which signifies redemption and deliverance. Just as the lamb's blood offered protection to the Israelites, in the New Testament, the sacrificial nature of the "slain Lamb" symbolizes the offering made to redeem humanity from sin.

The vision presented in Revelation 5 describes an extraordinary celestial scene where praise is showered upon this Lamb in a magnificent display. Notably, the multitude of angels speaking in different languages reflects the universality of the message, hinting at a glorious future where all creation recognizes this Lamb’s transformative role. It's a remarkable celebration in the heart of Heaven!

One interesting tidbit: the phrase “Worthy is the Lamb” pops up in some powerful worship music today. Songs like “Worthy is the Lamb” by Perkins bring a modern twist to these ancient proclamations, maybe igniting hearts today much like they lit up the throngs in John's vision centuries ago.

Finally, it's noteworthy how the number of angels “thousands upon thousands” raises questions about heavenly hosts. Many Biblical scholars see this on symbolic scales suggesting infinity, signifying the countless souls united in the recognition of this momentous truth; each one adds to a timeless chant resonating through ages. The nature of worship itself, then, becomes an invitation for all of humanity to join this celestial chorus!