Hebrews 7:11

If therefore there was perfection by the Levitical priesthood (for under that the people had the law given to them), what farther need was there that another priest should arise after the order of Melchisedec, and not be called after the order of Aaron?

Hebrews 8:7

For if that first covenant had been faultless, there would have been no place sought for a second.

Galatians 2:21

I do not set at nought the grace of God; for if righteousness came by the law, truly Christ hath died in vain.

Hebrews 5:6

As he saith also in another passage, "Thou art priest forever after the order of Melchisedec;"

Hebrews 7:17-19

For the testimony is, Thou art a priest for ever after the order of Melchisedec.

Galatians 4:3

So we also, when we were infants, were in bondage under the first elementary principles of the world:

Galatians 4:9

But now after having known God, or rather being known of God, how turn ye back again to those weak and beggarly elements, to which again a second time ye desire to be in bondage?

Colossians 2:10-17

and ye are complete in him, who is the head of all principality and power:

Hebrews 5:10

publicly proclaimed of God high-priest after the order of Melchisedec.

Hebrews 6:20

into which the forerunner for us is entered, even Jesus, made after the order of Melchisedec an high-priest for ever.

Hebrews 7:15

and it is yet more abundantly evident, that there should arise another priest after the likeness of Melchisedec,

Hebrews 7:21

(for they indeed were made priests without an oath; but he with an oath, by him who said unto him, "The Lord hath sworn, and will not repent, Thou art a priest for ever after the order of Melchisedec:")

Hebrews 8:10-13

For this is the covenant which I will make with the house of Israel after those days, saith the Lord; giving my laws to their understanding, even on their hearts will I inscribe them: and I will be to them a God, and they shall be to me a people.

Hebrews 10:1-4

NOW the law, having a shadow of the good things which were to come, not the very substance of the things, cannot possibly, by the same sacrifices which they offer year by year continually, make those perfect who approach [God];

Treasury of Scripture Knowledge

Summary

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?

Bible References

Perfection

Hebrews 7:18
For there is indeed an abrogation of the preceding command, because of its weakness and inutility.
Hebrews 8:7
For if that first covenant had been faultless, there would have been no place sought for a second.
Hebrews 10:1
NOW the law, having a shadow of the good things which were to come, not the very substance of the things, cannot possibly, by the same sacrifices which they offer year by year continually, make those perfect who approach [God];
Galatians 2:21
I do not set at nought the grace of God; for if righteousness came by the law, truly Christ hath died in vain.
Galatians 4:3
So we also, when we were infants, were in bondage under the first elementary principles of the world:
Colossians 2:10
and ye are complete in him, who is the head of all principality and power:

What

Hebrews 7:26
For such an high-priest was suitable to us, holy, inoffensive, spotless, separate from sinners, and made higher than the heavens:

Another

Hebrews 7:15
and it is yet more abundantly evident, that there should arise another priest after the likeness of Melchisedec,
Hebrews 5:6
As he saith also in another passage, "Thou art priest forever after the order of Melchisedec;"
Hebrews 6:20
into which the forerunner for us is entered, even Jesus, made after the order of Melchisedec an high-priest for ever.