'Faithful Witness' in the Bible

[It is also] from Jesus Christ, who is the Faithful Witness [to the truth], the Firstborn from the dead [i.e., the first One raised never to die again], the Ruler of the kings of the world. May there be honor and power forever and ever to Christ, who loved us and released us from our sins by His blood [Note: Some manuscripts say "washed us" since the two words are spelled almost alike].

I know where you are living; [it is] where Satan's throne is. And [I know] that you are holding on firmly to my name, and did not deny [your] faith in me, even in the days of my faithful witness Antipas [Note: The Greek word here for witness is "martyr"], who was killed there where you are, where Satan lives.