Дварим 6:5 Каббала: Zohar, Ohr Ne'erav, Sha'arei Kedusha & Kuntres Mattan Torah

But he who, recounting his neighbour’s good points, omits to bless him, will be the first to incur heavenly displeasure. Whereas he who does so bless will receive blessings from above. The man’s blessing, moreover, must be given not grudgingly, but generously and with a good heart, as God above all desires man’s good heart.¹v. T. B. Sanhedrin, 107a. How much more so must this be the case when a man offers praise to the Holy One, blessed be He! So Scripture says: “And thou shalt love the Lord thy God with all thy heart”, etc. (Ibid. 6, 5).

Beside this there are other commandments which cannot be properly fulfilled without knowledge of Torah and of this wondrous science. These [commandments] are the love and fear of God. They are commandments addressed to us in the Torah. [Concerning] love, it is written, You will love the Lord your God (Deut. 6:5). [Of] fear it is written, You will fear the Lord your God (Deut. 6:13, 10:20). If one does not comprehend the awesome majesty of His divinity, His separation from the rest of the existents, the origin of all that exists from Him as well as the number of degrees which exist until [His] providence reaches this lowly world, how can one fear Him?

Rabbi Simeon rejoiced and said: “O Lord, I have heard your report and am afraid (Hab. 3:2). There it is proper to be fearful. We [, however,] depend upon love. Thus it is written: You will love your fellow as yourself (Lev. 19:18). You will love the Lord your God (Deut. 6:5, 11:1). And I have loved you, says the Lord (Mal. 1:2).”