Sifra, Kedoshim, Section 1 10/ספרא·קדושים·פרשה א י׳

10) Which is fear? He shall not sit in his place, and he shall not speak in his place, and he shall not contradict his words. Which is honoring? Giving him to eat and to drink and clothing and covering and bringing in and taking out. "A man, his mother and his father you shall fear": I might think that if his father or mother told him to transgress one of the mitzvoth of the Torah he should heed them; it is, therefore, written "and My Sabbaths you shall keep" — You are all obliged to honor Me. (Vayikra 19:4) "Do not turn to the idols (elilim)": Do not turn to serve them (in thought). R. Yehudah says: Do not turn to scrutinize them.