Midrash su Salmi 39:7

All of the commandment that I command you today (Deuteronomy 8:1): This is what the verse stated (Proverbs 7:2), "Keep My commandments and live," since David said (Psalms 17:8), "Guard me like the apple of Your eye." Rabbi Yehudah of Sakhnin said, "There is [no piece of land fitting to plant] a fourth of a kav, which does not include nine kav of bad spirits." And Rabbi Yehoshua ben Levi said, "And they all have a veil over their faces." How is [it possible for people to avoid injury from them]? A man walks and [an angel] goes out in front of him and says, "Move to the sides before the likeness of the Holy One, blessed be He," as it is stated (Psalms 39:7), "Man walks in an image."