The foundation of foundations and the pillar of all wisdom is, to know that there is Primal Existence, that He mamtzi all that exists, and that all beings from heaven and earth, and what is between them, only exist by the truth of His Being.

This is as the prophet says: "God, Lord is truth" (Jer. 10.10); He alone is the Truth, and no other possesses a truth similar to His Truth, This is indicated in the Torah as it says: "There is none other than Him" (Deut. 4.39), meaning, there is no other true being, besides Him, like Him.

You shall love GOD your Lord with all your heart and with all your soul and with all your might.

It is a commandment to love and fear this glorious and awesome God, for it is said: "You shall love God your Lord" (Deut. 6,5); and it is said: "God your Lord you shall fear." (Ibid. 6, 13).

And what is the way to love and fear Him? When one contemplates His works, and His great and wondrous creations, and sees through them His wonderful, unique and infinite wisdom, he will immediately love, praise and exalt and become possessed of a great longing to know the Great Name, as David said: "My soul thirsts for God, the living God" (Ps. 42,2).

(3) It is a commandment upon every person to love each and every Jew as himself, as it is stated, "You shall love your neighbor as yourself" (Leviticus 19:18). Therefore one needs to speak praises of [the other] and to be as careful with his money as one is with one's own money and [as one] desires his own honor. Whoever gains honor through the disgrace of his fellow has no portion in the world to come.

(2) The one who serves [God] out of love is involved in Torah study and in the commandments and goes in the paths of wisdom, not for the sake of something in the world and on account of fear from [resulting] evil, and not in order to acquire a good but rather, he does the truth on account of its being the truth - and in the end, the good will come because of it. And this virtue is a very great virtue and not every sage merits it. And it is the virtue of our father, Avraham, who the Holy One, blessed be He, called he who loved Him, since he only served [God] out of love. And it is the virtue that the Holy One, blessed be He, commanded us through Moshe, as it says, And you shall love the Lord, your God (Deuteronomy 6:5). And when a man loves the Lord with an appropriate love, automatically he does all of the commandments out of love.

(3) What is the appropriate Love? It is that a person should love God with a great and very excessive love, until his souls is bound up in love of God and he focuses on it constantly as if he were lovesick and could not take his mind off of some woman, whether sitting, standing, even when he eats and drinks. Beyond this, love of God should be in their hearts constantly, as we were commanded: with all your heart and with all your soul (Deut. 6:5). Thus [King] Solomon said, as a metaphor, for I am lovesick (Song of Songs 2:5), for all of Song of Songs is a metaphor for this matter.

(4) The First Sages said (Nedarim 62a), "Lest you will say, 'behold I will study Torah in order that I will become rich, in order that I will be called 'rabbi,' in order that I will receive reward in the World to Come,' [the verse comes to] teach [the opposite, when it] says (Deuteronomy 11:13), to love the Lord - everything that you do, you should only do out of love." And the sages also said (Avodah Zara 19a), "Greatly desire His commandments, not the reward of His commandments." And so would the greatest Sages especially command their most understanding and brightest students (Avot 1:3), "'Do not be like slaves, that serve their master, etc.,' but rather, because He is the Master, it is fitting to serve him." That is to say, "serve Him out of love.

(5) Anyone who engages in Torah in order to receive a reward, or so that misfortune will not befall him, engages in Torah not for its own sake; but anyone who engages in it not from Fear and not from a desire to receive reward – she engages in it for its own sake. Our sages taught: A person should certainly engage in Torah even not for its own sake, since engagement not for its own sake leads to engagement for its own sake. Therefore when we teach children and women and generally ignorant people – we only teach them to serve out of Fear and in order to receive a reward. Once their understanding deepens and they gain additional wisdom, then we reveal this secret to them little by little and accustom them to this concept gently until they grasp and understand and serve God through Love.

(6) It is a clearly known matter, that Love of the Holy Blessed One is not bound up in a person’s heart until she engages it constantly as is appropriate, and abandons everything else in the world but this, as God commanded and said: with all your heart and with all your soul (Deut. 6:5). Love will be according to understanding: if [understanding] is slight, [love] will be slight, and if [understanding] is great, [love] will be great. Therefore a person must set aside [time] for himself to understand and grasp the wisdom and understanding that his Creator provides him according to each person’s ability to understand and grasp, as we have explained in Laws of the Foundations of Torah.

But you, Israel, My servant, Jacob, whom I have chosen, Seed of Abraham My beloved— You whom I drew from the ends of the earth And called from its far corners, To whom I said: You are My servant; I chose you, I have not rejected you— Fear not, for I am with you, Be not frightened, for I am your God; I strengthen you and I help you, I uphold you with My victorious right hand. Shamed and chagrined shall be All who contend with you; They who strive with you Shall become as naught and shall perish. You may seek, but shall not find Those who struggle with you; Less than nothing shall be The men who battle against you. For I the LORD am your God, Who grasped your right hand, Who say to you: Have no fear; I will be your help. Fear not, O worm Jacob, O men of Israel: I will help you —declares the LORD— I your Redeemer, the Holy One of Israel.

But how may one discover the way to love and fear Him?... And when he will contemplate all these matters,²Sifre, Deut. 6.5; Shabbat, 30–31. G. he will immediately reel back and become stricken with awe, and realize that he is an infinitesimal creature, humble and dark, standing with an insignificant and slight knowledge in the presence of the Complete Awareness, as David said: "For when I see Thy heavens, the wonderful works of Thy fingers, of what use is man that Thou mayest remember him?" (Ibid. 8,4). 

When Yitzhak grew old his eyes dimmed from seeing. 

...From the power of that seeing. When Abraham tied his son Yitzhak on the altar [Yitzhak] stared directly at the Shekhina...and when he aged he lost his sight.