The scripture says different.
Galatians 3:20-21 (KJV)
[SUP]20 [/SUP]Now a mediator is not a mediator of one, but God is one.
[SUP]21 [/SUP]Is the law then against the promises of God? God forbid: for if there had been a law given which could have given life, verily righteousness should have been by the law.
Hebrews 9:15 (KJV)
[SUP]15 [/SUP]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.
The first Testament contains the writings of Moses, and the prophets. Jesus is the mediator so the two fit together as God has intended from the beginning. Jesus clearly tells the Pharisees that without believing the writings of Moses, they wouldn't believe His Words.
John 5:46-47 (KJV)
[SUP]46 [/SUP]For had ye believed Moses, ye would have believed me: for he wrote of me.
[SUP]47 [/SUP]But if ye believe not his writings, how shall ye believe my words?
Heb. 7
11Now if perfection was through the Levitical priesthood (for on the basis of it the people received the Law), what further need was there for another priest to arise according to the order of Melchizedek, and not be designated according to the order of Aaron?
12For when the priesthood is changed, of necessity there takes place a change of law also.
13For the one concerning whom these things are spoken belongs to another tribe, from which no one has officiated at the altar.
14For it is evident that our Lord was descended from Judah, a tribe with reference to which Moses spoke nothing concerning priests.
15And this is clearer still, if another priest arises according to the likeness of Melchizedek,
16who has become such not on the basis of a law of physical requirement, but
according to the power of an indestructible life.
17For it is witnessed of Him,
“THOU ART A PRIEST FOREVER
ACCORDING TO THE ORDER OF MELCHIZEDEK.”
18For, on the one hand, there is a setting aside of a former commandment because of its weakness and uselessness
19(for the Law made nothing perfect), and on the other hand there is a bringing in of a better hope, through which we draw near to God.
20And inasmuch as it was not without an oath
21(for they indeed became priests without an oath, but He with an oath through the One who said to Him,
“THE LORD HAS SWORN
AND WILL NOT CHANGE HIS MIND,
‘THOU ART A PRIEST FOREVER’”);
22so much the more also Jesus has become the guarantee of a
better covenant.
23And the former priests, on the one hand, existed in greater numbers, because they were prevented by death from continuing,
24but He, on the other hand, because He abides forever, holds His priesthood permanently.
25Hence, also, He is able to save forever those who draw near to God through Him, since He always lives to make intercession for them.
Heb. 8
7For if that first covenant had been faultless, there would have been no occasion sought for a
second.
13When He said, “A
new covenant,”
He has made the first obsolete. But whatever is becoming obsolete and growing old is ready to disappear.
Heb. 9
15And for this reason
He is the mediator of a new covenant, in order that since a death has taken place for the redemption of the transgressions that were committed under the first covenant, those who have been called may receive the promise of the eternal inheritance.
Heb. 10
19Since therefore, brethren, we have confidence to enter the holy place by the blood of Jesus,
20by a
new and living way which He inaugurated for us through the veil, that is, His flesh,
21and since we have a great priest over the house of God,
22let us draw near with a sincere heart in full assurance of faith, having our hearts sprinkled clean from an evil conscience and our bodies washed with pure water.
23Let us hold fast the confession of our hope without wavering, for
He who promised is faithful
I recommend reading Hebrews from start to finish for a fuller understanding of just what God did in establishing this NEW covenant.
It's new! 
Based on better promises, and a perfect High Priest!
Perfectly and FULLY provided by Christ's sacrifice.
Man has no part in this new covenant because (as the first covenant proved) man cannot uphold his end of the deal.
Ever.
When our parents sinned in the garden, did God tell them to sacrifice an animal for covering? No. HE did it.
When Abraham was too terrified to walk between the slaughtered animals, Who came and did it?
It's all about this plan God had from the foundation of the world to redeem us.
4But when the fulness of the time came, God sent forth His Son, born of a woman, born under the Law,
5in order that He might redeem those who were under the Law, that we might receive the adoption as sons. (Gal 4)
17For the Law was given through Moses; grace and truth were realized through Jesus Christ. (John 1)
