Deuteronomy 6

Before Moses was to depart from Israel, you would expect that he would provide what he considered to be of greatest importance.  Thus with all the desires of his heart he instructs them -

"Hear therefore, O Israel, and observe to do it; that it may be well with thee, and that ye may increase mightily, as the LORD God of thy fathers hath promised thee, in the land that floweth with milk and honey.
4 Hear, O Israel: The LORD our God is one LORD:
5 And thou shalt love the LORD thy God with all thine heart, and with all thy soul, and with all thy might.
6 And these words, which I command thee this day, shall be in thine heart..."  (Old Testament | Deuteronomy 6:3 - 6)

Even -

"Thou shalt fear the LORD thy God, and serve him, and shalt swear by his name."  (Old Testament | Deuteronomy 6:13)

...or in words, keep the covenants you have made with Hims.  And knowing that he would not be around forever, Moses instructs -

"...thou shalt teach them diligently unto thy children, and shalt talk of them when thou sittest in thine house, and when thou walkest by the way, and when thou liest down, and when thou risest up."  (Old Testament | Deuteronomy 6:7)

Because of the covenants the Lord made with their fathers -

"For thou art an holy people unto the LORD thy God: the LORD thy God hath chosen thee to be a special people unto himself, above all people that are upon the face of the earth.
7 The LORD did not set his love upon you, nor choose you, because ye were more in number than any people; for ye were the fewest of all people:
8 But because the LORD loved you, and because he would keep the oath which he had sworn unto your fathers..."  (Old Testament | Deuteronomy 7:6 - 8)

"Know therefore that the LORD thy God, he is God, the faithful God, which keepeth covenant and mercy with them that love him and keep his commandments to a thousand generations..."  (Old Testament | Deuteronomy 7:9)

And the promise is, if we love Him with all our heart, might, mind, and strength, that is  -

"...if ye hearken to these judgments, and keep, and do them, that the LORD thy God shall keep unto thee the covenant and the mercy which he sware unto thy fathers:
13 And he will love thee, and bless thee, and multiply thee: he will also bless the fruit of thy womb, and the fruit of thy land, thy corn, and thy wine, and thine oil, the increase of thy kine, and the flocks of thy sheep, in the land which he sware unto thy fathers to give thee.
14 Thou shalt be blessed above all people..."  (Old Testament | Deuteronomy 7:12 - 14)

These promises are to all that love Him and receive His ordinances and covenants.