Why are both Jesus and Satan referred to as the morning star?
The apparent overlap between these two titles is one of contrast, not identity — and the key lies in the original languages and the very different purposes behind each passage.
In Revelation 22:16, the Lord Jesus declares Himself to be "the root and the offspring of David, and the bright and morning star." In Isaiah 14:12, the king of Babylon is taunted in his fall: "How art thou fallen from heaven, O Lucifer, son of the morning!" The Hebrew word there is helel — rendered "Lucifer" in the Latin — meaning "light-bringer" or "shining one."
Morrish's Bible Dictionary makes the distinction succinctly. On Lucifer:
Morrish's Bible DictionaryName, signifying in Latin 'light-bringer,' being a translation of the Hebrew word, helel, associated with 'morning star,' given in irony to the king of Babylon, because in his pride he said he would exalt his throne above the stars of God. Isa. 14:12.
And on the Morning Star as a title of Christ:
the Morning StarThis heralds in 'the day.' The Lord Jesus is the bright and morning star, and He makes Himself known to the saints in that heavenly character, and Peter speaks of its rising in their hearts, though they wait for His appearing, to usher in full blessing on earth, when He will shine forth as the SUN OF RIGHTEOUSNESS. Rev. 2:28; Rev. 22:16; Mal. 4:2.
William Kelly directly addresses the contrast between the two uses. In the natural world, the morning star is the herald that appears just before the dawn. In prophecy and in the gospel, this symbol is taken up in opposite directions:
William KellyThe day-star of prophecy is rather the title of the Lord's enemy (Lucifer) as seen in Isaiah 14. The day-star that the Christian ought to have arising within is Christ while He is outside the world in heaven, before He shines as Sun of Righteousness upon the earth. By the gospel day dawns, and the day-star or heavenly hope of Christ arises in the heart while the Christian is here, as he enters into Christian privilege by the truth.
Edward Dennett, in a dedicated paper on this subject, explains what the morning star signifies when applied to Christ — it is the harbinger of the coming day of glory:
Edward DennettThe symbol could only mean one thing naturally — namely, that the morning star not only precedes, but that it is also the presage or the harbinger of the day. This being so, it is easy to gather the sense of its application to Christ. That is, when used of Him, it must likewise signify that He, as so set forth, is the herald of the day; that just as the watcher during the night is assured when he beholds the morning star that the night is passing away, and that the sun will soon arise and flood the world with its brilliant rays, so when the Morning Star has arisen in our hearts, we have the certain knowledge that "the night is far spent" and "the day is at hand."
C.J. Davis states the contrast plainly:
C.J. DavisThe "morning star" or "day star" of the New Testament is Christ Himself as the person we wait for. To our affections He now shines forth. The watchers in the night see Him and enjoy Him by faith in their hearts, till He is seen by their eyes. But the day or morning star (Lucifer) of prophecy (Isa. 14) is the king of Babylon to be destroyed by Jehovah.
J.N. Darby sees Isaiah 14's "Lucifer" as not merely the historical king of Babylon but a figure of Antichrist — the ultimate counterfeit of Christ:
J.N. DarbyLucifer in this is Antichrist, and it will be found, in every particular, to be the counterpart of Christ, in his assumptions in all the characters of His glory.
Julius Von Poseck traces the deeper history behind the title — an angelic being of original splendour whose pride brought about his ruin:
Julius Von PoseckThat once exalted and bright angelic spirit, whose name was "Lucifer," or "Day Star," and "Son of the Morning," had said in his heart, "I will ascend into heaven; I will exalt my throne above the stars of God … I will be like the most High" (Isa. 14.) … That sin of disobedience, which characterized the fall of "Lucifer, the Day Star," turned that beautiful "covering cherub" into the arch deceiver.
Synthesis
The two are not really called by the same title. The Hebrew helel in Isaiah 14 is applied in bitter irony — a taunt-song over a proud king (and, behind him, the spiritual power animating him) who aspired to a glory not his own: "You who claimed to be the herald of the dawn have been cast down to the pit." The title mocks the pretension; it does not affirm the reality.
Christ, by contrast, is the bright and morning star — genuinely and by right. The morning star appears before the sun rises; just so, Christ makes Himself known to believers in their hearts now, during the long night of His absence, before He appears publicly as the Sun of Righteousness to bless the whole earth. As Darby puts it, the one is the counterfeit who grasped at every character of Christ's glory; the Other is the true Light who holds it by right and will bring in the everlasting day.