Musar do Liczb 24:18

Ephron, or rather the people of his town also hinted at that fact when they said in 23,15 נשיא אלוקים אתה בתוכנו, "you are a prince in our midst." They realized that while Abraham represented the essence of what was good, Ishmael represented the קליפה on the "right," Esau that on the "left." We here view grandchildren as being in the same class as children. Isaac, who is described in the grace after meals as the recipient of the blessing מכל, has only one קליפה, Esau attached to him. Jacob, on the other hand, is totally free of any קליפה sticking to him. He represents the tree of life in the centre of the garden.