This note is interpretation, not translation. Revelation opens by calling Jesus “the trustworthy witness” (1:5), and the same title comes back three times. This note follows it, and the psalm it comes from.
From the psalm of David’s covenant. “Jesus the Anointed — the trustworthy witness, the firstborn out of the dead, the ruler over the kings of the earth” (1:5). The green marker there is Psalm 89:27: “I will make him firstborn, highest among the kings of the earth.” Ten verses later the same psalm says of David’s line, “like the moon it will be established forever, a faithful witness in the sky” (89:37; 89:38 in the Hebrew), and the Greek translation of that line is ho martys en ouranō pistos, “the faithful witness in heaven.” So all three of John’s titles at 1:5 are in one psalm: the faithful witness, the firstborn, the highest over the kings of the earth. The marker names the firstborn and the kings; the faithful witness comes from the same psalm, ten verses on.
What a witness is. The Greek-word note at 1:5 says it: martys is a witness in the ordinary legal sense, someone who saw it and will say so; the meaning “martyr” came later. Jesus said why He came: “for this I was born, and for this I came into the world, to testify to the truth” (John 18:37), and He did it in front of Pilate, “who testified the good confession before Pontius Pilate” (1 Timothy 6:13). “We speak what we know and testify to what we have seen” (John 3:11). Proverbs: “a truthful witness saves lives” (Proverbs 14:25). God said to Israel, “you are my witnesses” (Isaiah 43:10), and of David’s son, “I have given him as a witness to the peoples, a leader and commander for the peoples” (55:4).
The title, three more times. To Laodicea: “These are the words of the Amen, the trustworthy and true witness” (3:14), with Isaiah 65:16’s “God of Amen” marked there. On the white horse: “the one sitting on it is called Faithful and True, and he judges and makes war in fairness” (19:11). And He gives His own title away. At Pergamum: “Antipas, my trustworthy witness, who was killed among you” (2:13). The one witness calls a man in a hard city by His own name.
His witnesses. The book’s people share it. The two witnesses prophesy in sackcloth (11:3); the woman is “drunk with the blood of God’s people and the blood of the witnesses of Jesus” (17:6); and they beat the accuser “by the blood of the Lamb and by the message they testified to” (12:11). “The testimony of Jesus is the spirit of prophecy” (19:10). Against the accuser who lies about God’s people day and night (12:10), the trustworthy witness tells the truth, and gives His people His word to tell.