Every so often, we hear of a well-meaning Christian attempting a “Jesus Fast” – a forty-day renunciation of food that recalls the time Jesus spends in the wilderness (cf. Matt 4:2; Mk 1:13; Lk 4:2). Undertaking this fast sometimes leads to health issues and even death (a quick internet search reveals a surprising number of such unfortunate incidents). What these strict attempts at messianic replication miss, however, is the fact that “forty” has a specific symbolic meaning in Jewish thought; the number signifies a period of judgment, so that the Gospels’ reference to forty days is more about the nature of Jesus’ testing than it is about calendrical time. In assigning “forty days” to Yeshua’s fast, the Gospel writers locate their Messiah within a numerical Jewish tradition that highlights his experience as the subject of proper judgment.
Jesus’ forty days in the wilderness recalls Israel’s forty years in the Sinai desert after the exodus—a time that Scripture refers to explicitly as a period of divine judgment or testing of the peoples’ faithfulness: “The Lord your God has led you these forty (ארבעים; ‘arba’im) years in the wilderness, that he might humble you, testing (נסה; nasah) you to know what was in your heart, whether you would keep his commandments or not” (Deut 8:2). In his discourse with the devil, Jesus quotes the very next verse in Deuteronomy (Deut 8:3; cf. Matt 4:4; Lk 4:4), which shows that Jesus’ forty days accomplishes the same end as the Israelites’ forty years: Yeshua is “tested” (πειράζω; peirádzo) in order to see whether he would keep God’s commandments—and, of course, he does.
Beyond the forty years that Israel spends in the wilderness, it does not take much scriptural study to see that the number forty symbolizes judgment: God judges the earth with the flood rains for “forty days and forty nights” (ארבעים יום וארבעים לילה; ‘arba’im yom v’arba’im laylah; cf. Gen 7:4, 12, 17; 8:6); Moses, like Jesus, fasts on Sinai for “forty days and forty nights” as he receives the legal statutes of the Torah (Exod 34:28), which would be the standard for “righteous judgment” (משׁפט צדק; mishpat tsedeq; Deut 16:18); and Deborah, the best judge in Israel’s history, brings peace to the land for “forty years” (ארבעים שׁנה;‘arba’im shanah; Judg 5:31; cf. 3:11; 8:28). In light of this numerical symbolism, the meaning of “forty” is far more important than the number itself. Therefore, instead of testing the limits of our bodies with a literal forty-day fast, Bible readers should focus on the theological “testing” to which the number forty points. Understanding forty days/years as a time of “judgment” highlights the reason for Jesus’ wilderness wanderings and the level of Jesus’ success in following God.