מדרש על אבות 6:4

It says elsewhere in Scripture in reference to the Oral Law: Neither is it found in the land of the living (ibid. 28:13). What is the meaning of the verse Neither is it found in the land of the living? Does it mean that the Oral Law is found only among the deceased? Indeed not. It means that the Oral Law is not found among those who pursue the pleasures of this world—its passions, its glory, or its greatness, but only among those who deprive themselves for its sake, as it is said: This is the law; when a man dieth in a tent (Num. 19:40). The following is the path that leads to an understanding of the law: “A morsel of bread with salt shall you eat; a measure of water shall you drink; upon the earth shall you sleep; a life of hardship shall you lead; and in the law shall you labor.”⁵Pirkei Avot 6:4. The Holy One, blessed be He, established His covenant with Israel through the Oral Law, as it is said: According to the tenor of these words have I made a covenant with thee and with Israel (Exod. 34:27).