Many have taken comfort in the promise found in the letter to the Hebrews:
Hebrews 13:8 (NASB) Jesus Christ is the same yesterday and today and forever.
But is the comfort taken from this passage rooted in a proper understanding of the verse? Often it is interpreted to mean that Jesus is unchanging from eternity past to eternity future, and thus, many see it as an affirmation that Jesus is God: he pre-existed yesterday, he exists today, and he will exist forever. The verse is seen as a parallel passage to texts like Malachi 3:6 where God declares:
Malachi 3:6 (NASB) “For I, the LORD, do not change; therefore you, O sons of Jacob, are not consumed. (emphasis added)
Hebrews 13:8, however, says nothing about Jesus’ having a divine nature, much less one that doesn’t change. Nor does it contain a reference or title signifying deity. On the contrary, the author acknowledges that Jesus is the Christ, that is, the Messiah or the one anointed by God, and not God himself.
Jesus Christ, the Same Yesterday and Today and Forever
Those who see the passage as proof of Jesus’ immutability fail to recall that the Savior experienced significant change even within a Trinitarian framework. For example, a pre-incarnate Jesus, who was without form, took on flesh at his incarnation. He went from possessing one nature to two. Moreover, he went from 
being an immortal being, to a mortal who died, to a resurrected, glorified, immortal man. As God, the theory goes, he would have possessed all wisdom. However, Scripture records that he increased in wisdom, as well as in favor, with God. Last but not least, his rank or position also changed. He was supposedly God Almighty but took a demotion to become man, but was then exalted back to a heavenly throne in the end. Thus, even in a Trinitarian world, Jesus underwent change.
Professor and author, John Wilson, further elaborates on the changes Jesus underwent:
As to his person or nature, Jesus Christ was not immutable. He underwent all those changes to which human nature is subject. His feelings, his sentiments, and his actions–his poverty and his sufferings–his birth, his death, and his resurrection, and the glorious reward which he obtained from his heavenly Father for his unremitted labours [sic] in the great cause of human happiness–all of which form the mighty and animating theme of the New Testament–evince, to a moral certainty, that he was not unchangeable.[1] (emphasis added)
The rebuttal that is often offered is that Jesus only experienced change in his human nature, while his divine nature remained unchanged. However, Scripture never teaches the doctrine of Christ’s supposed dual natures. In fact, Biblical scholar and professor, Charles Feinberg, admits that the doctrine, also known as the hypostatic union, cannot be found in Scripture:
When we seek to understand the hypostatic union in its implications, those features and factors involved in it, it is not long before we find that the New Testament contains no systematic or formal setting forth of the doctrine of the two natures in the Person of Christ.[2] (emphasis added)
On the contrary, these ideas developed over centuries, partly in an effort to resolve contradictions that arose, especially during the fourth century, when Jesus was ultimately declared to be God and co-equal with the Father. Contradictions such as how could Jesus, if he is the omniscient God, not know the day or the hour of his return? Or, how could Jesus die since God is immortal and cannot die? Or, how can Jesus’ will differ from that of the Father’s if they are both God? It wasn’t until the Council of Chalcedon in 451 A.D. that the conflict surrounding the hypostatic union was said to be resolved. In reality, however, the conflict continues to this day because the contradictions remain.
Examining the Context
If the phrase yesterday and today and forever is not a reference to Christ’s immutability, then what does it mean? In order to properly understand the text, we 
must examine the context in which it appears:
Hebrews 13:7-9 (NASB) Remember those who led you, who spoke the word of God to you; and considering the result of their conduct, imitate their faith. 8 Jesus Christ is the same yesterday and today and forever. 9 Do not be carried away by varied and strange teachings; for it is good for the heart to be strengthened by grace, not by foods, through which those who were so occupied were not benefited.
The author exhorts his readers to remember their leaders who had shared God’s word with them and to imitate their faith. He also warns them not to be carried away by various strange teachings, which in subsequent verses alludes to teachings associated with the Law.[3] Indeed, the entire book is an exhortation to Hellenized Jews who had come to faith, to remain in Christ and not return to the Mosaic way of life.[4] Sandwiched in-between the exhortation to remember and imitate those who spoke God’s word to them, and the warning not to be carried away by certain teaching is the phrase about Jesus. The context, therefore, is about being consistent in one’s faith in Jesus the Christ. The author of the well known Vincent’s Word Studies, even though a Trinitarian, agrees with this assessment:
No doubt the old teachers believed in the unchangeableness of Jesus Christ; but that fact is not represented as the subject of their faith, which would be irrelevant and somewhat flat. The emphatic point of the statement is Christ. They lived and died in the faith that Jesus is The Christ – the Messiah. The readers were tempted to surrender this faith and to return to Judaism which denied Jesus’s [sic] messiahship. Hence the writer says, “hold fast and imitate their faith in Jesus as the Christ. He is ever the same. He must be to you, today, what he was to them, yesterday, and will be forever to the heavenly hosts – Christ.[5] (emphasis added)
The Meaning of Yesterday
As mentioned earlier, some propose that the word yesterday is a reference to Jesus’ pre-existence in heaven. The word in Greek is echthes (or chthes), and it appears a mere three times in the New Testament: John 4:52, Acts 7:28, and Hebrews 13:8. In the first two occurrences, the word is undoubtedly used to denote the day before today:
John 4:52 (NASB) So he inquired of them the hour when he began to get better. Then they said to him, “Yesterday at the seventh hour the fever left him.” (emphasis added)
Acts 7:28-29 (NASB) ‘You do not mean to kill me as you killed the Egyptian yesterday, do you?’ 29 “At this remark, Moses fled and became an alien in the land of Midian, where he became the father of two sons. (emphasis added)
Strong’s Concordance defines echthes as: yesterday; by extension in time past or hitherto (until now). Thayer’s Greek Lexicon defines it as: of time just past. The Complete Word Dictionary of the New Testament says echthes is: an adverb of time; yesterday; also refers to past or former time.[6]
Twice, the word echthes is used in the Septuagint, the Greek translation of the Old Testament. In both occurrences, it is used to signify a non-specific length of time in the past that could still be recalled by those in the present:
Genesis 31:2 (NASB) Jacob saw the attitude of Laban, and behold, it was not friendly toward him as formerly. (emphasis added)
2 Samuel 3:17 (NASB) Now Abner had consultation with the elders of Israel, saying, “In times past you were seeking for David to be king over you.” (emphasis added)
Based on its usage in the New Testament and the Septuagint, yesterday (echthes) is never used to denote time before time. In other words, the period before the world began in which Jesus is theorized to have pre-existed. Therefore, to say that yesterday in Hebrews 13:8 refers to Jesus’ supposed eternality would be inconsistent with its definition and Biblical usage.
John Calvin, although a staunch Trinitarian, understood that the text under review was not a proof for Jesus’ theoretical pre-existence. Rather, the reformer understood it to refer to the knowledge of Christ:
It hence appears that the Apostle is not speaking of the eternal existence of Christ, but of that knowledge of him which was possessed by the godly in all ages, and was the perpetual foundation of the Church. It is indeed certain that Christ existed before he manifested his power; but the question is, what is the subject of the Apostle. Then I say he refers to quality, so to speak, and not to essence;[7] (emphasis added)
What’s more, pastor and scholar, Thomas Constable, in his expository notes of the Bible, offers his understanding of the text:
Jesus Christ is the content of the message that the leaders had preached to these hearers (cf. Hebrews 13:7). That message and its hero is what this writer had urged his readers not to abandon. The leaders had preached the Word of God to these readers, and that preaching culminated in Jesus Christ.
“Yesterday” the original leaders preached Jesus Christ, even as the writer does now; the present time can tolerate no other approach to the grace of God (Hebrews 2:9). “Forever” recalls the quality of the redemption secured by Jesus Christ and of the priesthood of Christ: it is “eternal.”[8] (emphasis added)
Conclusion
While more scholars could be quoted, these should be sufficient to demonstrate the meaning of Hebrews 13:8. Regardless of any nuances in the interpretations presented here, the main point in each is that the phrase Jesus Christ is the same yesterday and today and forever does not refer to a pre-existent Jesus, nor is it proof of deity. Rather, to put it in the broader context of Hebrews, Jesus is still the Christ sent by God to mediate a better covenant by means of his own life’s blood.[9] It was sufficient then, and it is sufficient now. In this truth, we can find great comfort.
[1] John Wilson, Scripture Proofs and Scriptural Illustrations of Unitarianism, (London, 1846), p. 227.
[2] Charles Lee Feinberg, “The Hypostatic Union,” Bibliotheca sacra 92, no. 368 (1935): 412.
[3] A.W. Pink, Commentary on John and Hebrews, Hebrews 13:9, StudyLight.org, accessed 12-12-19, https://www.studylight.org/commentaries/awp/hebrews-13.html
[4] Numerous scholars from a variety of backgrounds attest to this. For example, the Wycliffe Bible Commentary, Chuck Smith Bible Commentary, Vincent Word Studies, the introduction to Hebrews in the Ryrie Study Bible, Harper Study Bible, Amplified Study Bible, Jack Hayford’s Study Bible, NASB Study Bible, etc.
[5] Marvin Vincent, Vincent Word Studies, StudyLight.org, accessed 12-13-19.
[6] Spiros Zodhiates, The Complete Word Study Dictionary of the New Testament, Strong’s #5504, (Chattanooga, TN:AMG Publishers, 1993), p. 1475.
[7] John Calvin, Calvin’s Commentary on the Bible, Hebrews 13:8, StudyLight.org, accessed 12-10-19.
[8] Thomas Constable, Expository Notes of Dr. Thomas Constable, Hebrews 13:8, StudyLight.org, accessed 12-10-19.
[9] Hebrews 7:22; 8:6 and 12:24.
