Zohar 2:26b-27a

Jewish Mysticism
R. Eliezer began to expound- It is written, “And know this day, and consider it in your hearts, that the Lord is God” (Deut. 4-39). This verse should have been written as follows- “And know this day that the Lord is God, and consider it in your hearts.” Moreover, it should have said “consider it in your heart” libbekha. Yet Moses said- If you want to understand this and know that the Lord is God, then consider it in your hearts, levavekha, and you will know it. “Your hearts”— the good inclination and the evil inclination, for one is contained in the other and they are one. Then you will know that the Lord is God for one is contained in the other, and they are one. Thus it is written “consider it in your hearts” in order to know the matter. Moreover, R. Eliezer said- the wicked make a blemish above. What [is] the blemish? For the left is not contained in the right, the evil inclination is not contained in the good inclination on account of the sins of humanity. . . . And thus it says, “And consider it in your hearts,” to contain them as one, the left in the right.

Translated by Elliot Wolfson in “Light Through Darkness- The Ideal of Human Perfection in the Zohar,” Harvard Theological Review 81 (1988)- 73-95.