The Zohar, Chapter “Ve’Eleh Toldot Itzhak (These Are the Generations of Isaac),” Item 30: Jacob knew that Esau would cling to that Slant Serpent. For this reason, he followed him in all his actions like another Slant Serpent, opposite him, cleverly and shrewdly.
It is precisely the desire to receive pleasure that teaches us to be shrewd. It teaches us how to work with the same desire and lie to it. After all, the desire to bestow does not have wisdom or a mind; it has no Light of Hochma (the Light of Wisdom). It’s meant for the desire to receive pleasure. Therefore, in particular, the serpent is smart. We need to learn wisdom from it for the right line. This is called “help against him” since the serpent, itself, teaches us the right line and how to work with it. It teaches us how to kill it, extract only medicine from its venom, and to work with this medicine for the desire for the intention to bestow.