VII. Heb 13:8 Jesus Christ is the same (ο αυτος ) yesterday, today, and forever.
First let everyone slap themselves and wake up. Jesus Christ was not immutable. He was a baby became a man and died. These are very real changes. This is not a reference to metaphysical nature of Jesus and certainly not a reference to the human nature of Jesus. The term Christ is the same as Messiah in the Old Testament. The Messiah has always been a man who would save Israel.
Tertullian would wrestle with the idea of Jesus changing and offer the solution of the two natures of Jesus. In what became the forerunner of the Chalcedonian Creed (c.451) Tertullian ( c. 155 – c. 240 AD) was struggling with the Platonic idea of God being unable to change with the clear presentation of Jesus changing. 
Luke 2:52 (NIV)
52 And Jesus grew in wisdom and stature, and in favor with God and man.
Jesus had two natures, a human nature and a divine nature. This is called the hypostatic union as confirmed by the Council of Chalcedon. Tertullian and the council agreed that Christ had two natures, one human and one divine.
As such Tertullian could maintain that even though the human nature of Jesus suffered change the god nature of Jesus did not change. Classical theism has never denied that the human nature of Jesus did change. This is confirmed by Catholicism, Lutheranism, Calvinism and Wesleyanism.
 Tertullian. “Against Praxaeus.” Translated by Peter Holmes. In vol. 3 of The Ante-Nicene Fathers, edited by A. Cleveland Coxe, Alexander Roberts, and James Donaldson. American reprint of the Edinburgh Edition. New York: Charles Scribner’s Sons, 1918. Chapter 27.
“and the Flesh, on the other hand, exhibited the affections which belong to it. It was hungry under the devil’s temptation, thirsty with the Samaritan woman, wept over Lazarus, was troubled even unto death, and at last actually died.”
 Tertullian “and the Flesh, on the other hand, exhibited the affections which belong to it. It was hungry under the devil’s temptation, thirsty with the Samaritan woman, wept over Lazarus, was troubled even unto death, and at last actually died.”
 Tertullian “We see plainly the twofold state, which is not confounded, but conjoined in One Person—Jesus, God and Man. …Of them Jesus consists—Man, of the flesh; of the Spirit, God
What does Hebrew 13:8 mean that God is the same. Almost every translation confirms the use of the word same. Does “same” refer the metaphysical concept of the substance of God or the knowledge of God. Since God is immutable he cannot change his knowledge or his substance or does change refer to something else?
Heb 13:8 Jesus Christ is the same (ο αυτος ) yesterday, today, and forever.
The words in the Greek translated “the same” are literally, “the him.” There is an article and a third person pronoun, in this case it is called an intensive pronoun. This is usually translated “the same” but the same is not immutability. Robertson, a famous Biblical grammarian, explains the use of αυτος and other intensive pronouns under a section entitled The Intensive and Identical Pronoun . He writes, “the use of αυτος was originally “purely anaphoric… As the third personal pronoun it was, of course, anaphoric. The intensive use is more emphatic.”
All pronouns are anaphoric, meaning “an expression the interpretation of which depends upon another expression.” With pronouns the word the pronoun is replacing is called the antecedent. As an illustration, consider the following statements. “The fisherman was late. He was sleeping.” The pronoun “he” stands for its antecedent, the fisherman.
The same construction is used in Romans 10:12. What is implied in the statement is that there is a “Lord of the Jews” and a “Lord of the Greeks.” But this is the same Lord. Not this is the immutable lord, but this is the same Lord. There is a sense of identity and sense of anaphoric use of the pronoun. The same Lord anaphorically refers to the “Lord of the Jews” and a “Lord of the Greeks,” but this is identical to the Lord who is over all.
Romans 10:12 For there is no distinction between Jew and Greek, for the same Lord (ο αυτος κυριος) over all is rich to all who call upon Him.
The authority on ancient Greek, Herbert Weir Symth, [i] refers to the pronoun as meaning the same, but in what sense? Is “same” referring to immutability? Obviously not, since he quotes a man using αὐτός meaing “same.” The idea is not immutability but in some respects the man has not changed but his friend has changed.
- After the article, in the attributive position (1154),αὐτός in any case means same.
a. So as a predicate: ἐγὼ μὲν ὁ αὐτός εἰμι, ἱ_μεῖς δὲ μεταβάλλετε I am the same, it is you who changed.
[i] Herbert Weir Smyth A Greek Grammar for Colleges revised Gordon M. Messing (Cambridge, MA 1980 (1856), cited by section number
In the same manner the Hebrews text is saying in some respects Jesus does not change but in some respects he does change. Obviously Jesus changed. He was a baby, he became a man, he died, and he was resurrected. In some manners Jesus did not change. The context of Hebrews 13 determines what these manners are.
Again, what is the context of Hebrews 13?
Hebrews 13: 1-8 Let brotherly love continue. 2 Do not forget to entertain strangers, for by so doing some have unwittingly entertained angels. 3 Remember the prisoners as if chained with them—those who are mistreated—since you yourselves are in the body also. 4 Marriage is honorable among all, and the bed undefiled; but fornicators and adulterers God will judge. 5 Let your conduct be without covetousness; be content with such things as you have. For He Himself has said, “I will never leave you nor forsake you.” 6 So we may boldly say:
“The Lord is my helper; I will not fear. What can man do to me?”
7 Remember those who rule over you, who have spoken the word of God to you, whose faith follow, considering the outcome of their conduct. 8 Jesus Christ is the same yesterday, today, and forever. 9 Do not be carried about[c] with various and strange doctrines. For it is good that the heart be established by grace, not with foods which have not profited those who have been occupied with them.
The theme of the chapter is doing good works to be established in Jesus Christ. This same Christ has said “I will never leave you nor forsake you,” but this is a quote from Deuteronomy 31:6.
David speaks of the same Christ who promised you “The Lord is my helper” but this is a quote from Psalm 118:6. The point of Hebrews 13:8 is that Jesus Christ is the God who is making the promises in the Old Testament. This same God who is Jesus Christ, did not change in this manner, in present, nor will he change in the future. Jesus Christ will never forsake his chosen, in the past or the present or the future.
The classical theological interpretation to make this a claim about the immutability of Christ’s essence or his attributes is ludicrous. It would be an isolated statement in the midst of an extended logical exhortation to good works.
This is not a copula “is” in the Greek text. A better translation is “Jesus Christ, yesterday, today, the same one (who made the promises) and forever.” Of course the “who made the promises” is the antecedent of the pronoun “he” and the phrase was supplied by the translator in order to understand the verse. It is the same he as the one making the promises.