A.T. Robertson Commentary Revelation 5:13

"And every created thing which is in the heaven, and on the earth, and under the earth, and on the sea, and all things are in them, heard I saying, Unto him that sitteth on the throne, and unto the Lamb, [be] the blessing, and the honor, and the glory, and the dominion, for ever and ever." — Revelation 5:13 (ASV)

Every created thing (παν κτισμα). Every creature in a still wider antiphonal circle beyond the circle of angels (from κτιζω, for which see 1 Timothy 4:4; James 1:18), from all the four great fields of life (in heaven, upon the earth, under the earth as in verse 3, with on the sea επ της θαλασσης added). No created thing is left out. This universal chorus of praise to Christ from all created life reminds one of the profound mystical passage in Ro 8:20-22 concerning the sympathetic agony of creation (κτισις) in hope of freedom from the bondage of corruption. If the trail of the serpent is on all creation, it will be ultimately thrown off.

Saying (λεγοντας). Masculine (construction according to sense, personifying the created things) if genuine, though some MSS. have λεγοντα (grammatical gender agreeing with παντα) present active participle of λεγω, to say.

And to the Lamb (κα τω αρνιω). Dative case. Praise and worship are rendered to the Lamb precisely as to God on the throne. Note separate articles here in the doxology as in 4:11 and the addition of το κρατος (active power) in place of ισχυς (reserve of strength) in 5:12.