In 1 Timothy 6:16 why does Paul characterize Jesus as “Immortal”?
By definition "immortality" means one cannot die; immortal. However, 1 Timothy 6:16 (KJV) the Greek word ἀθανασίαν is translated as "Immortal"
In context of Paul's writing and his contrast to humans , these words "who alone possesses immortality" apply to Jesus and not to God. Jesus now alone possesses immortality and in the invisible heavens, he is unseen to human eyes.
1 Timothy 6:14-16 (NASB)
14 "That you keep the commandment without stain or reproach until the
appearing of our Lord Jesus Christ, 15 which He will bring about at
the proper time—He who is the blessed and only Sovereign, the King of
kings and Lord of lords, 16 who alone possesses immortality and dwells
in unapproachable light, whom no man has seen or can see. To Him be
honor and eternal dominion! Amen."
Jesus by being faithful to the end, was granded the gift "immortality", something he did not posses before his ascension to heaven, is shown by the inspired words of Paul, who wrote:
Romans 6:9 (NASB)
9 "Knowing that Christ, having been raised from the dead, is never to
die again; death no longer is master over Him."
Similarly in the book of Revelation, John wrote Jesus words to him:
Revelation 1:17-18 (NASB)
17 "When I saw Him, I fell at His feet like a dead man. And He placed
His right hand on me, saying, “Do not be afraid; I am the first and
the last, 18 and the living One; and I was dead, and behold, I am
alive forevermore, and I have the keys of death and of Hades."
Paul in describing Jesus as "the King of kings and Lord of lords, who alone possesses immortality." (1 Tim. 6:15-16) clearly shows that Jesus is distinct from the other human kings and lords and High priests of Israel that were mortal and died. Similarly Daniel wrote,And to Him "Jesus" was given supreme authority Glory and a kingdom:
Daniel 7:14 (NASB)
14 “And to Him was given dominion, Glory and a kingdom, That all the
peoples, nations and men of every [b]language Might serve Him. His
dominion is an everlasting dominion Which will not pass away; And His
kingdom is one Which will not be destroyed."