Likutei Moharan, Part II 4:4/ליקוטי מוהר"ן·תנינא ד׳:ד׳

14. However, one has to take in the lovingkindness gradually. This is because it is impossible to receive lovingkindness in abundance, as this would cause one to cease to exist—[as in:] They cannot bear an abundance of good (Taanit 23a). One has to create a container and a conduit through which to receive the lovingkindness. This is accomplished through fear of Heaven, which makes a ChaKiKah (engraving) and a conduit through which to take in the lovingkindness, as in “and a m’ChoKeK (lawgiver) from between his feet” (Genesis 49:10). “Feet” alludes to fear of Heaven, which signifies the end, as it is written “In the end, all things having been considered: Fear the Lord” (Ecclesiastes 12:13). In other words, fear of Heaven, which corresponds to the feet, creates an engraving and conduit in order to receive the lovingkindness.

2This is the meaning of “and behold! the staff of Aharon of the house of Levi had blossomed” (Numbers 17:23). The lovingkindness, Aharon’s trait, has to be received by the container, which conceptually is fear of Heaven, the side of Levi, as in “with the saving strengths of His right arm” (Psalms 20:7).