Context of the verse
Revelation 4.1 marks a transition: John moves from the letters to the Churches (chs. 2–3) to the great heavenly vision.
The text says: “After this I looked, and behold, a door was open in heaven. The first voice that I had heard, like the sound of a trumpet, said to me: Come up here…”
Why does John specify “the voice that I had heard”?
Narrative continuity: John refers back to the voice heard in Revelation 1.10–11, that of the glorified Christ who had given him the first revelation. This creates a common thread between the visions.
Divine authority: By recalling that it is the same voice, John stresses that the origin of the revelation is single and reliable: it is Christ who speaks, not a new source.
A landmark for the reader: The expression helps the reader recognize the voice as familiar, already introduced, and therefore trustworthy. This avoids any confusion with the other voices that will appear in the book (angels, creatures, etc.).
Pedagogical dimension: John shows that the revelation is not a series of isolated visions, but a coherent discourse guided by the same Lord.
Symbolism
The voice is described “like a trumpet”: an image of clarity, power and solemn summons.
The recalling of this voice reinforces the idea that John is led step by step in a pedagogical progression: first the vision of Christ (ch. 1), then the Churches (chs. 2–3), then the heavenly throne (ch. 4).
In summary: John says “the voice that I had heard” to ensure continuity, to recall the authority of Christ, and to guide the reader through a coherent revelation. It is a way of showing that everything that follows proceeds from the same divine source.