The Old Covenant was based upon the promise of the people. Ex 24:7. The New Covenant is based upon the promise of God:
"But this shall be the Covenant that I will make with the house of Israel; after those days, saith the Lord, I will put My law in their inward parts, and write it in their hearts; and I will be their God and they shall be My people." Jer 31:31-34.
"WHO is He speaking of? Paul answers, "Now to Abraham and his seed were the promises made, He saith not, And to thy seeds as of many: but as of one, And to thy seed which is Christ." "And if ye be Christ's, then are ye Abraham's seed and heirs according to the promise." Ga 3:16,29.
"Know ye therefore, that they which be of faith, the same are the children of Abraham." Ga 3:7
"For HE IS NOT A JEW, who is one outwardly; neither is that circumcision which is outward in the flesh: BUT HE IS A JEW, which is one inwardly; and circumcision is that of the heart, in the spirit, and not in the letter; whose praise is not of men, but of God." Rom 2:28,29.
"...For they are not all Israel, which are of Israel: Neither because they are the seed of Abraham, are they all children: but in Isaac shall thy seed be called. That is, they which are the children of the flesh, these are not the children of God: but the children of the promise are counted for seed." Rom 9:6-8.
The promises were made through Abraham to the children of promise (Rom 9:6-8), who are justified by faith - whether Jew or Gentile.
When Moses struck the rock and disobeyed the Lord, God charged him with unbelief. When the children of Israel disobeyed the Lord, they were not able to enter The Promised Land, because of unbelief. Heb 3:19. Unbelief comes out of an evil heart. Heb 3:12.
Disobedience = Unbelief
Obedience = Faith
Rom 16:29 refers to "the obedience of faith."
"By faith Abraham...obeyed." Heb 11:8
"Do we then make void the law through faith? God forbid: yea, we establish the law." Rom 3:31
God spoke to Abraham: "And I will make thy seed to multiply as the stars of heaven, and will give unto thy seed all these countries; and in thy seed shall all the nations of the earth be blessed.
BECAUSE that Abraham obeyed My Voice (HIS WORD), and kept MY CHARGE, MY COMMANDMENTS, MY STATUTES, and MY LAWS." Gen 26:4,5.
"Even so, faith if it hath not works is dead, being alone. Yea, a man may say, Thou hast faith and I have works: shew me thy faith without thy works, and I will shew thee my faith by my works.
Thou believest that there is one God; thou doest well: the devils also believe and tremble. But wilt thou know, O vain man, that faith without works is dead?
Was not Abraham our father JUSTIFIED BY WORKS, when he had offered Isaac his son upon the altar (In response to the command of God)?
SEEST THOU HOW FAITH WROUGHT WITH HIS WORKS, AND BY WORKS WAS FAITH MADE PERFECT?
And the Scripture was fulfilled which saith ABRAHAM BELIEVED GOD (faith & obedience), and it was imputed to him for righteousness: and he was call the Friend of God.
YE SEE THEN HOW THAT BY WORKS A MAN IS JUSTIFIED, AND NOT BY FAITH ONLY...For as the body without the spirit is dead, so faith without works is dead also." James 2.
In Psalm 119, the word, "Word," is used interchangeably with, "law," "commandments," "judgments," "precepts," "statutes," "testimonies."
HIS WORD IS HIS LAW
"A NEW HEART also will I give you, and A NEW SPIRIT will I put within you: and I will take away the stony heart out of your flesh, and I will give you an heart of flesh.
And I WILL PUT MY SPIRIT WITHIN YOU, and CAUSE YOU to walk in My statutes, and ye shall keep My judgments and do them." Ezek 36:26,27.
When we are born again, having His Spirit within us, He empowers us to obey His Word/His law.
"But be ye DOERS of the Word, and not hearers, only, DECEIVING your own selves." Ja 1:22.