Answer: We check with the mind what we feel in our heart. A heart is all the desires of a person, and I need to check who controls my desires: the will to receive with an intention in order to receive or with an intention in order to bestow. The will to receive is always there; it is the substance of creation, but I must examine for what I am working.
This examination is done only through the group. In our physical world we cannot measure anything without a scale of measurement. We require some unit of measurement: a meter, a kilogram, Hertz, a measurement scale with which I will be able to measure and weigh some phenomenon.
How can I weigh a desire and my intention that controls it? This is only possible depending on how I adhere to the group and associate myself with the whole. Through this I can measure myself and change something within me. Otherwise, I will always be mistaken.
Therefore, “And you shall love your neighbor as yourself” is called the fundamental rule in the Torah for it controls everything. If I do not place myself correctly relative to society, I will not be able to see where I am at all. With my measurements, I will not be able to discern any error, neither the smallest nor the largest.
From the Preparation to the Daily Kabbalah Lesson 3/31/13