27 January 2025

Jesus’s 40-day fast.

Matthew 4.2, Luke 4.2.

Whenever we see people fast (and usually pray; they kinda go together) in the Old Testament, they’re either mourning, repenting, or strongly petitioning God. But after the Spirit sent Jesus to the wilderness to be tempted, we see Jesus fasting—

Matthew 4.2 KWL
Fasting 40 days and 40 nights,
Jesus is famished afterwards.
Luke 4.2 KWL
…to be tested by the devil 40 days.
Jesus is eating nothing in those days,
and is famished by the end of them.

—and we know he’s not repenting, for he has nothing to repent; we’re fairly sure he’s not mourning; so most Christians figure he’s strongly petitioning his Father. He’s about to have a Satan-encounter, and even though he expects to win (’cause come on; he’s God) he gave up his omniscience when he became human, and doesn’t know what Satan’ll bring to their meeting. So the best thing anyone can do in that circumstance, is pray up!

And it definitely wouldn’t hurt to fast. Well, hurt spiritually. With some obvious exceptions, like hypoglycemia, you’re gonna physically be fine till the second hunger pangs kick in. Then you’re gonna be weak. But this isn’t a physical battle anyway; it’s not like that scene in C.S. Lewis’s novel Perelandra, in which Ransom literally has to beat the devil-possessed Weston to death. That was messed up; that was based on the fleshly limitations of Lewis’s imagination. Jesus knows better than to think physical force stops a spiritual one. Fasting is actually a way of renouncing physical force: We make ourselves weak so that God can make us spiritually strong. We use the Spirit’s fruit of self-control to pursue the Spirit all the more.

That’s why Jesus fasted: He wanted to be overprepared to overmatch the devil. So he deprived himself, and as the scripture says, he was famished afterwards. But in his spirit, he was mightier than ever.

Forty days.

Both Matthew and Luke state Jesus’s fast lasted 40 days: He ate nothing. Matthew adds “and 40 nights,” to make it clear Jesus wasn’t merely doing a daytime fast, like Muslims do for Ramadan: He ate nothing for 40 days straight.

There are those Christians who assume Jesus ate nothing and drank nothing during his fast—again, like Muslims do for Ramadan. Thing is, humans can’t go without water for that long. Blood pressure drops, organs get damaged, kidneys fail, we faint, we die. Takes about five days. So unless the Father supernaturally intervened, like the LORD did with Moses, Ex 34.28 he had to drink something.

Christians figure Jesus was baptized in winter, around Epiphany, when the Jordan would have been in flood stage. Which means Jesus’s 40-day fast, which happened right afterwards, would also have taken place in winter. There’d be rain. Creeks wouldn’t have dried up yet. Wherever Jesus was staying, he had access to water. Doctors say if you do a total fast, drink plenty of water; probably Jesus did just that.

I’ve read a lot about long-term fasting. Some of the advice is mighty contradictory. Some of ’em recommend you keep yourself busy, so you can get your mind off how hungry you are. Others recommend you don’t keep yourself busy; your body needs to conserve energy, ’cause after 12 hours without food, you’re burning body fat, and you only have so much! (Well, unless you’re American. We have plenty.) But everybody recommends lots of water, and lots of sleep.

Christians have all sorts of theories about what Jesus did during those 40 days. Most assume he just spent it in a cave somewhere, praying non-stop. Yeah, okay… but what did he do while praying? ’Cause you can do other things while praying. Monks prefer manual labor, ’cause you seldom have to think while you’re working, so you can pray instead. Jesus didn’t have to just sit and stare at the wall the whole time he spoke with his Father; he coulda whittled. Or brought a Hebrew copy of Deuteronomy to memorize word-for-word, ’cause you notice in the gospels he did know it word-for-word.

But you also notice Luke 4.2 says Jesus was ἡμέρας τεσσεράκοντα πειραζόμενος ὑπὸ τοῦ διαβόλου/yméras tesserákonta peiradzómenos ypó tu diavólu, “40 days tested by the devil.” Makes it sound like all 40 days, Satan showed up and tempted him. Which… might be exactly what happened. Every day, Jesus was tempted to eat something, or perform the sort of miracle that’d go viral, or give up and capitulate to Satan.

And every day, he refused. And if you thought it’d be harder to resist the temptation the hungrier you got, man alive do you not know how fasting works. It actually gets easier.

I’ve heard preachers claim humans can fast no more than 40 days. I’ve also heard doctors point out that’s not so: Everybody’s different. Some of us can only fast a week and no more; some of us can fast for months. Really it all comes down to how much body fat we have on us. Once we have no more body fat to burn, our bodies start consuming its own muscle tissue, and now we’re in physical trouble.

I don’t know whether Jesus had only 40 days of body fat on him—he’s not American, remember—or whether he picked 40 days as a long-enough length of time to make his point that he was easily able to resist Satan. Either way, after 40 days it was time to tell it, “Get thee behind me,” Lk 4.8 and end the temptation, end the fast, eat till he got his strength back (maybe with some angelic help, Mk 1.13, Mt 4.11), then go back to civilization and begin his ministry.