זוהר בראשית — דף קצח ע”ב

The Zohar continues on the days of evil: groups of harmful forces draw near those who defile their way and lead them down the very road they wished to take, while one who comes to purify himself is helped. It explains the washing of the hands in the morning, the right by the left, so that the right may rule and leave no room for the evil inclination. David examined his sins and therefore pursued his enemies; Asa pursued and the Holy One, blessed be He, struck; Jehoshaphat sang; Hezekiah stayed at home and the angel struck the camp of Assyria. Joseph recognized his brothers and had compassion on them, whereas Simeon and Levi, from the side of severe judgment, had none. “Why should I fear?”: David did not fear, and “my heels” are the sins a person tramples underfoot.