After John heard the loud voice commanding him to write down what he saw, we read,
12 Then I turned to see the voice that was speaking to me, and on turning I saw seven golden lampstands, 13 and in the midst of the lampstands one like a son of man, clothed with a long robe and with a golden sash around his chest. 14 The hairs of his head were white, like white wool, like snow. His eyes were like a flame of fire, 15 his feet were like burnished bronze, refined in a furnace, and his voice was like the roar of many waters. 16 In his right hand he held seven stars, from his mouth came a sharp two-edged sword, and his face was like the sun shining in full strength. (Revelation 1:12-16)
So, now we see the source of that voice. John turns around and sees seven golden lampstands. Remember that this is a vision, so a lot of this imagery is going to be symbolic. These seven golden lampstands represent the seven churches that were mentioned in verse 11.
In the midst of these lampstands, John sees "one like a son of man, clothed with a long robe and with a golden sash around his chest" (v. 12). The phrase "son of man" was commonly used to talk about a human being. This was one of the Savior's favorite designations of Himself. So, John sees someone who looks like a man, and sure enough, we'll shortly see that this person is Jesus Christ Himself.
It's comforting to read that this man is "in the midst of the lampstands" (v. 13). It reminds us that Jesus Himself is in the midst of His churches. For He has said, "...behold, I am with you always, to the end of the age" (Matthew 28:20).
The Savior, here, is "clothed with a long robe." Long, flowing robes were worn by kings. His rank is further displayed in the "golden sash around His chest" (v. 13).
We also see that "the hairs of His head were white, like white wool, like snow" (v. 14). The idea here is resplendence and glory. It hearkens back to the transfiguration in Matthew 17:2: "And he was transfigured before them, and his face shone like the sun, and his clothes became white as light."
We then see that "His eyes were like a flame of fire" (v. 14). God's eyes are described in Daniel 10:6 as being like fire, all-searching, and all-penetrating. This also may be referring to His indignation against sin.
Verse 15 tells us, "His feet were like burnished bronze, refined in a furnace." This is talking about the same kind of resplendence. His feet were like brass that had turned bright white in the process of burning.
His voice was like the roar of many waters. A booming, glorious voice.
Verse 16 continues, "In His right hand He held seven stars." These seven stars, we'll later read, are seven angels or messengers, likely those who'll deliver Christ's message to these churches.
John goes on, "from His mouth came a sharp two-edged sword" (v. 16), either referring to His word, which is described as a two-edged sword in (Hebrews 4:12) or alluding to His judgment against sin.
Finally, we see that "His face was like the sun shining in full strength" (v. 16). This completes the picture of the resplendent, glorious Christ whom John was beholding. How different He looks here than when He was a baby in a manger or a mangled man on the cross. Our Savior is glorious, resplendent in beauty, and greatly to be praised. And the messages that He's about to send out are not only for those seven churches but for us also. Let us listen to Him.