Definition and Nature:
Heavenly praise refers to the worship and adoration directed towards God by celestial beings and the redeemed in the heavenly realms. It is characterized by its purity, intensity, and perpetual nature, reflecting the glory and majesty of God. This form of praise is a central theme in the Bible, illustrating the ultimate purpose and joy of all creation.

Biblical Instances:

1. Angelic Praise:
The Bible frequently depicts angels as beings who continually praise God. In Isaiah 6:3, the seraphim call out to one another, "Holy, holy, holy is the LORD of Hosts; His glory fills the whole earth." This scene emphasizes the holiness and omnipresence of God, as acknowledged by the heavenly hosts.

2. Heavenly Worship in Revelation:
The Book of Revelation provides vivid imagery of heavenly praise. Revelation 4:8 describes the four living creatures, each with six wings, who "day and night never stop saying: 'Holy, holy, holy is the Lord God Almighty, who was, and is, and is to come!'" This ceaseless worship underscores the eternal nature of God's sovereignty and the unending adoration He receives.

Further, in Revelation 5:11-12, John witnesses a multitude of angels around the throne, numbering "myriads of myriads and thousands of thousands," proclaiming with a loud voice, "Worthy is the Lamb who was slain, to receive power and riches and wisdom and strength and honor and glory and blessing!" This passage highlights the centrality of Christ's redemptive work as a focal point of heavenly praise.

3. The Praise of the Redeemed:
The redeemed also participate in heavenly praise. Revelation 7:9-10 describes a great multitude from every nation, tribe, people, and language standing before the throne and before the Lamb, crying out, "Salvation to our God, who sits on the throne, and to the Lamb!" This scene reflects the inclusivity and unity of the redeemed in their worship of God and the Lamb.

Theological Significance:

1. Reflection of God's Glory:
Heavenly praise serves as a reflection of God's infinite glory and majesty. It is a response to His holiness, power, and love, as well as His redemptive acts through Jesus Christ. The continuous nature of this praise signifies the eternal worthiness of God to receive honor and adoration.

2. Model for Earthly Worship:
The depictions of heavenly praise in Scripture provide a model for earthly worship. Believers are encouraged to emulate the reverence, joy, and devotion seen in the heavenly realms. Hebrews 12:22-24 invites believers to approach "Mount Zion, the city of the living God, the heavenly Jerusalem," joining the assembly of angels in joyful praise.

3. Anticipation of Eternal Worship:
Heavenly praise also points to the future hope of eternal worship in God's presence. The scenes in Revelation offer a glimpse of the ultimate fulfillment of God's redemptive plan, where all creation will join in perfect harmony to glorify Him forever.

Conclusion:
Heavenly praise is a profound expression of worship that transcends time and space, uniting angels and the redeemed in the adoration of God. It serves as both an inspiration and a goal for believers, calling them to participate in the eternal chorus of praise that glorifies the Creator and Redeemer.