EXOD408 The most difficult of all the commandments of the Torah to fulfill completely, according to the second-century sage Simeon bar Yohai, is the obligation of a child to honor and to revere his or her mother and father. Midrash Tanhuma, Solomon Buber, ed. (Vilna, 1885), "Ekev," no. 3.p. 9a. In this regard, the following story is told of Rabbi Tarfon: "Rabbi Tarfon had a mother. When she wished to mount into bed, he would bend down to let her ascend [by stepping on him, and when she wished to descend, she would do so by stepping on him]. He went to the Academy and boasted of his observance of filial piety. [Whereupon] his colleague said to him: You have not even reached half the honor [due her]. Kiddushin 31b. See also P. Peah 1:1. As it is stated in the Ten Commandments, the obligation of a child toward his or her parents seems clear enough [this verse, Deuteronomy 5:16]. This commandment differs from the other nine, because only in the case of this commandment is a reason given, i.e., "That you may long endure...." In other words, the reason for observance is the promise of longevity and the threat of a curtailed life for nonobservance.