Charles Ellicott Commentary Revelation 4:1

"After these things I saw, and behold, a door opened in heaven, and the first voice that I heard, [a voice] as of a trumpet speaking with me, one saying, Come up hither, and I will show thee the things which must come to pass hereafter." — Revelation 4:1 (ASV)

After this (better, these things) I looked (literally, I saw; not “I looked,” as though the prophet turned his gaze then towards it), and, look, a door was opened (or, set open) in heaven. He did not look and see a door opening; he saw, and look! the door stood open.

There are differences as well as similarities between this vision and others where glimpses into heaven were given to prophets and saints. In Ezekiel’s vision, and in the scene of Matthew 3:16 (Acts 10:11), the heavens divide; in this vision, a door stands open.

The way into the presence of God lies open (Hebrews 10:19–20); all who have faith may enter. In the minds of such people, the thoughts of the heavenly will mingle with the sorrows of the earthly, and the calm of security will be theirs (Psalms 46:5).

But the scenes of earth’s troubles will always be dispiriting to those who cannot reach the heavenly viewpoint.

And the first voice (or, indeed, the first voice) which I heard was like a trumpet talking with me; (even one) which said, Come up here, and I will show you (the) things which must take place after this. The first voice spoken of here is the voice which the Apostle had heard in the opening vision (Revelation 1:10); he heard, and recognized that trumpet-like voice again.

It is strange that anyone should have maintained that this is not the voice of Christ. It is admitted that it must be the same as the voice of Revelation 1:10, but it is said that the voice of Christ is heard afterwards (Revelation 1:15), not as a trumpet, but as the voice of many waters.

The answer is simple: the voice of Christ has many tones, and the voice like a trumpet said, I am Alpha and Omega, the first and the last .