33 Continue your study of the witness borne by Moses; mark how diligently he seizes every opportunity of proclaiming the Lord and God. You take note of the passage, Hear, O Israel, the Lord your God is One. Note also the words of that Divine song of his; See, See, that I am the Lord, and there is no God beside Me. While God has been the Speaker throughout the poem, he ends with, Rejoice, you heavens, together with Him and let all the sons of God praise Him.
Rejoice, O you nations, with His people, and let all the Angels of God do Him honour. God is to be glorified by the Angels of God, and He says, For I am the Lord, and there is no God beside Me. For He is God the Only-begotten, and the title 'Only-begotten' excludes all partnership in that character, just as the title 'Unoriginate' denies that there is, in that regard, any who shares the character of the Unoriginate Father. The Son is One from One. There is none unoriginate except God the Unoriginate, and so likewise there is none only-begotten except God the Only-begotten.
They stand Each single and alone, being respectively the One Unoriginate and the One Only-begotten. And so They Two are One God, for between the One, and the One Who is His offspring there lies no gulf of difference of nature in the eternal Godhead. Therefore He must be worshipped by the sons of God and glorified by the angels of God. Honour and reverence is demanded for God from the sons and from the angels of God. Notice Who it is that shall receive this honour, and by whom it is to be paid.
It is God, and they are the sons and angels of God. And lest you should imagine that honour is not demanded for God Who shares our nature, but that Moses is thinking here of reverence due to God the Father—though, indeed, it is in the Son that the Father must be honoured— examine the words of the blessing bestowed by God upon Joseph, at the end of the same book. They are, And let the things that are well-pleasing to Him that appeared in the bush come upon the head and crown of Joseph. Thus God is to be worshipped by the sons of God; but God Who is Himself the Son of God.
And God is to be reverenced by the angels of God; but God Who is Himself the Angel of God. For God appeared from the bush as the Angel of God, and the prayer for Joseph is that he may receive such blessings as He shall please. He is none the less God because He is the Angel of God; and none the less the Angel of God because He is God. A clear indication is given of the Divine Persons; the line is definitely drawn between the Unbegotten and the Begotten. A revelation of the mysteries of heaven is granted, and we are taught not to dream of God as dwelling in solitude, when angels and sons of God shall worship Him, Who is God's Angel and His Son.
Source: On the Trinity (New Advent)