Revelation 4:2

I was in the spirit As Revelation 1:10 q.v. It is implied that he was caught up through the open door into Heaven, and saw what was going on above.

was set i.e. was there already not that he saw it put in its place. There is a description of the Throne of God in the apocryphal Book of Enoch, Revelation 14:17-20, very like this: probably St John had read it (cf. Judges 15), and his language shews quotations of it, as well as of the canonical passages in Ezekiel 1 and Daniel 7.

and one sat on the throne God the Father, not the Trinity: the presence of the other Persons being otherwise indicated, Revelation 4:5, and Revelation 4:6. It is intimated, though with an intentional vagueness, that the Divine Presence was symbolised by a human Form, as in Isaiah 6:1; Isaiah 6:5; Ezekiel 1:26 sq.; Daniel 7:9: contrast Deuteronomy 4:12, but compare Exodus 24:10-11; Exodus 33:23. Apparently God revealed Himself by such symbols to men whom He had educated to such a point that they should not imagine them to be morethan symbols. Therefore perhaps to attempt to include representations of the Father in the range of Christian art is rather of dangerous boldness than ipso factoillegitimate: see on this question Ruskin's Modern Painters, Part III. Sec. ii. Chap. v. § 7.