Where does it say HE can be the only one and will ALWAYS be the only one??
The Melchisedek Priesthood is
the priest of The Most High God and is a unique and eternal Priesthood: (Genesis 14:18) (Psalm 110:4)
Jesus became our Eternal High Priest after the order of Melchisedek when He offered Himself as a sacrifice once and for all - for the sins of mankind. There can only be one Eternal High Priest who can go before God on behalf of the sins of the people.
Hebrews, Chapter 5, verses:
8: Though he were a Son, yet learned he obedience by the things which he suffered;
9:
And being made perfect, he became the author of eternal salvation unto all them that obey him;
10:
Called of God an high priest after the order of Melchisedec.
Hebrews, Chapter 7, verses:
11: If therefore perfection were by the Levitical priesthood, (for under it the people received the law,) what further need was there that another priest should rise after the order of Melchisedec, and not be called after the order of Aaron?
12: For the priesthood being changed, there is made of necessity a change also of the law.
13: For he of whom these things are spoken pertaineth to another tribe, of which no man gave attendance at the altar.
14: For it is evident that our Lord sprang out of Juda; of which tribe Moses spake nothing concerning priesthood.
15:
And it is yet far more evident: for that after the similitude of Melchisedec there ariseth another priest,
16:
Who is made, not after the law of a carnal commandment, but after the power of an endless life.
17:
For he testifieth, Thou art a priest for ever after the order of Melchisedec.
18: For there is verily a disannulling of the commandment going before for the weakness and unprofitableness thereof.
19: For the law made nothing perfect, but the bringing in of a better hope did; by the which we draw nigh unto God.
20: And inasmuch as not without an oath he was made priest:
21: ( For those priests were made without an oath; but this with an oath by him that said unto him, The Lord sware and will not repent, Thou art a priest for ever after the order of Melchisedec: )
22:
By so much was Jesus made a surety of a better testament.
23: And they truly were many priests, because they were not suffered to continue by reason of death:
24:
But this man, because he continueth ever, hath an unchangeable priesthood.
25: Wherefore he is able also to save them to the uttermost that come unto God by him, seeing he ever liveth to make intercession for them.
26: For such an high priest became us, who is holy, harmless, undefiled, separate from sinners, and made higher than the heavens;
27:
Who needeth not daily, as those high priests, to offer up sacrifice, first for his own sins, and then for the people's: for this he did once, when he offered up himself.
28:
For the law maketh men high priests which have infirmity; but the word of the oath, which was since the law, maketh the Son, who is consecrated for evermore.
Hebrews, Chapter 8, verses:
1:
Now of the things which we have spoken this is the sum: We have such an high priest, who is set on the right hand of the throne of the Majesty in the heavens;
2: A minister of the sanctuary, and of the true tabernacle, which the Lord pitched, and not man.
3: For every high priest is ordained to offer gifts and sacrifices: wherefore it is of necessity that this man have somewhat also to offer.
4:
For if he were on earth, he should not be a priest, seeing that there are priests that offer gifts according to the law:
Hebrews, Chapter 9, verses:
6: Now when these things were thus ordained, the priests went always into the first tabernacle, accomplishing the service of God.
7: But into the second went the high priest alone once every year, not without blood, which he offered for himself, and for the errors of the people:
8: The Holy Ghost this signifying, that the way into the holiest of all was not yet made manifest, while as the first tabernacle was yet standing:
9: Which was a figure for the time then present, in which were offered both gifts and sacrifices, that could not make him that did the service perfect, as pertaining to the conscience;
10: Which stood only in meats and drinks, and divers washings, and carnal ordinances, imposed on them until the time of reformation.
11:
But Christ being come an high priest of good things to come, by a greater and more perfect tabernacle, not made with hands, that is to say, not of this building;
12:
Neither by the blood of goats and calves, but by his own blood he entered in once into the holy place, having obtained eternal redemption for us.
13: For if the blood of bulls and of goats, and the ashes of an heifer sprinkling the unclean, sanctifieth to the purifying of the flesh:
14: How much more shall the blood of Christ, who through the eternal Spirit offered himself without spot to God, purge your conscience from dead works to serve the living God?
15:
And for this cause he is the mediator of the new testament, that by means of death, for the redemption of the transgressions that were under the first testament, they which are called might receive the promise of eternal inheritance.
16: For where a testament is, there must also of necessity be the death of the testator.
17: For a testament is of force after men are dead: otherwise it is of no strength at all while the testator liveth.