Question: How could Jesus be our High Priest forever if He did not fulfill the Aaronic priesthood in Himself? Would not He have been under a curse if He had not inherited the High priesthood of Aaron?
Answer: I would like very much to answer your question cogently, but it is totally anti-biblical, and I am not sure where to grab onto it. You gave no citations (biblical or otherwise) so I cannot proceed with meaningful focus. Furthermore, its emphasis on a continuing Aaronic priesthood smacks of Mormonism—and this carries an entire category of problems. What I will do at the outset is to assure you that Jesus Christ did indeed fulfill Aaron’s (and everyone else’s) priesthood requirements, and to ensure you that his only curse, the curse of the cross, is also biblical and appropriate for the Savior.
Please understand that cultists like the Mormons and the Jehovah’s Witnesses use the Bible more for the illusion of credibility than for the developing of doctrine. They consider their own organization’s documents and/or traditions to be greater than or equal to Scripture. By way of contrast, nothing supersedes the Bible in my defense of orthodox Christianity. As a result, I must respond to all questions or comments from a biblical perspective. The result of this investment is that I am not necessarily conversant with every cultish book, document or idea, because understanding the Bible as God intends for us to understand it consumes my days. I tell you this because I honestly do not know where your ideas came from. If they came from extra-biblical sources, I do not know them. If they came from the Bible, then your interpretations of those uncited passages are wrong.
Jesus said that he came to fulfill the law—that this was his purpose. He did not do this as the Aaronic priests had done, performing continual sacrifices and making a yearly atonement for sin. But rather, he sacrificed himself—and in this he fulfilled the law…which is different than covering sin with a yearly atonement. I would ask then, if Jesus fulfilled the law, what purpose would an Aaronic priesthood serve?
“Do not think that I have come to abolish the Law or the Prophets; I have not come to abolish them but to fulfill them.” (Matthew 5:17, ESV)
The book of Hebrews teaches the superiority of Jesus’ priesthood, and for such a deep topic, the passages are quite approachable. I recommend that you study that entire book, watching for the priesthood issues in chapters 5 through 10 in particular. Indulge me while I paste in a relatively long passage from Hebrews chapter eleven, because this section speaks more clearly to your problem than ten thousand words from me.
“If the priesthood of Levi and Aaron, which provided the framework for the giving of the law, could really make people perfect, there wouldn’t have been need for a new priesthood like that of Melchizedek. But since it didn’t get the job done, there was a change of priesthood, which brought with it a radical new kind of law. There is no way of understanding this in terms of the old Levitical priesthood, which is why there is nothing in Jesus’ family tree connecting him with that priestly line. But the Melchizedek story provides a perfect analogy: Jesus, a priest like Melchizedek, not by genealogical descent but by the sheer force of resurrection life—he lives!—“priest forever in the royal order of Melchizedek.” The former way of doing things, a system of commandments that never worked out the way it was supposed to, was set aside; the law brought nothing to maturity. Another way—Jesus!—a way that does work, that brings us right into the presence of God, is put in its place. The old priesthood of Aaron perpetuated itself automatically, father to son, without explicit confirmation by God. But then God intervened and called this new, permanent priesthood into being with an added promise: God gave his word; he won’t take it back: “You’re the permanent priest.” This makes Jesus the guarantee of a far better way between us and God—one that really works! A new covenant. Earlier there were a lot of priests, for they died and had to be replaced. But Jesus’ priesthood is permanent. He’s there from now to eternity to save everyone who comes to God through him, always on the job to speak up for them. So now we have a high priest who perfectly fits our needs: completely holy, uncompromised by sin, with authority extending as high as God’s presence in heaven itself. Unlike the other high priests, he doesn’t have to offer sacrifices for his own sins every day before he can get around to us and our sins. He’s done it, once and for all: offered up himself as the sacrifice. The law appoints as high priests men who are never able to get the job done right. But this intervening command of God, which came later, appoints the Son, who is absolutely, eternally perfect.” (Hebrews 7:11–28, The Message)
How does this apply to your question? You asked, “How could Jesus be our High Priest forever…” and the answer is simple. Because the Bible tells us plainly that this is the case (Psa. 110:4, Heb. 6:20). You further asserted that Jesus “did not fulfill the Aaronic priesthood in Himself…” After reviewing Hebrews 7, are you still convinced that there are aspects of any priesthood which Jesus did not fulfill to God’s satisfaction? (Mk. 15:38, Gal. 3:23-25). Also note that Jesus is not connected to Aaron specifically as you assert. He is from the tribe of Judah, not Levi, and he therefore lacks the physical heritage for such a priesthood. By way of comparison, Melchizedek has an eternal priesthood that is not bound to flesh (Heb. 7:2-3), so taking on Aaron’s mantle would have been a big step backwards for Jesus. Why? Because the Aaronic priesthood was temporal whereas Jesus’ is eternal, and although some Aaronic style sacrifices continued for years after Jesus’ death (until the temple was destroyed in 70 AD), they continued in form only—their atoning efficacy eclipsed by the cross, and symbolized by the temple veil ripping in two (Mk 15:38). This meant that, unlike those of the old covenant, people under the new covenant would no longer be separated from God. And since Jesus’ blood served as the perfect and therefore final atonement, Aaron and his ilk were out of a job. Let’s move on to the curse.
Jesus Christ was under no other curse than the one God had given him—to be crucified. Please note that he became the curse because of us—and not by any fault of his own. Note also that the curse of the “tree” predated crucifixion by many centuries, and that Paul brings it from shadow to substance in Galatians.
“his body shall not remain all night on the tree, but you shall bury him the same day, for a hanged man is cursed by God. You shall not defile your land that the Lord your God is giving you for an inheritance.” (Deuteronomy 21:23, ESV)
“Christ redeemed us from the curse of the law by becoming a curse for us—for it is written, “Cursed is everyone who is hanged on a tree”—” (Galatians 3:13, ESV)
Moving on, I cannot leave this topic without a few comments on biblical typology, because this essential interpretive tool can help us determine which biblical entities have already been satisfied by Christ and which must continue. Typology is a specialized symbolism used in the Bible that connects an Old Testament item (known as the type) with a New Testament fulfillment (known as the antitype). Types usually reference the redemptive aspects of Jesus Christ, and in every case, the antitype (Jesus) is greater than the type, as is illustrated by Jesus’ teaching in the following verses.
“Or have you not read in the Law how on the Sabbath the priests in the temple profane the Sabbath and are guiltless? I tell you, something greater than the temple is here.” (Matthew 12:5–6, ESV)
In the above passages, the Old Testament temple is a type of Christ, and Jesus is the antitype of that temple. (Do not let the seemingly ambiguous “something greater” fool you. The context shows us that Jesus is referencing himself.) Why is he “greater?” Because his will be the once-and-for-all sacrifice, a sacrifice unequaled in any earthly temple. At the cross, the need for sacrifice was completed in Jesus Christ. Therefore, the temple was no longer needed. But the temple meant more than just the temple building. It included all aspects of its sacrificial system, which means that the altar, the animals and the Levitical priests were also no longer needed. It is critical to note, therefore, that Jesus was referencing the temple system in toto.
Not every priesthood has dissolved, however; another remains. It is the priesthood of the believer. But this is much different than Aaron’s priesthood. We are no mere altar servants. We are a people of his own—a royal priesthood no less!
“But you are a chosen race, a royal priesthood, a holy nation, a people for his own possession, that you may proclaim the excellencies of him who called you out of darkness into his marvelous light.” (1 Peter 2:9, ESV)
This priesthood is not about atonement (as in the Aaronic), but rather about ministering to God directly. Unlike the Old Testament priests, we have no limitations on our access to God. In fact, we believers have become the Temple of the Holy Spirit! (1 Cor. 6:19-20). As such, our sacrifices are not about atonement. They are about worship and service. We must lift up his name, continue in good works, spread the Gospel, intercede in prayer, etc.
Finally, concerning Jesus’ continuing priesthood, it is intercessory and not atoning. So, your notion that Jesus has yet to (or even ever needed to) intrinsically fulfill something of Aaron’s priesthood has no biblical teeth.
“Who is to condemn? Christ Jesus is the one who died—more than that, who was raised—who is at the right hand of God, who indeed is interceding for us.” (Romans 8:34, ESV)