Why Did Jesus Fast for 40 Days in the Wilderness?

The significance of "40 days" in the Old Testament.

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The Gospel of Matthew is believed to have been written with the Jewish audience in mind.

So when Matthew writes of Jesus fasting for “forty days and forty nights” in the wilderness before the devil tempted Him (Matthew 4:1-2), what would the “40 days” have brought to the mind of the Jewish reader? They were familiar with the Old Testament Scriptures, so their minds would consider “40 days” from that perspective.

As it turns out, “40 days” is used several times during significant events in the Old Testament.

How “40 Days” is used in the Old Testament.

The Bible uses the phrase “40 days” more than 20 times. Here we will notice the events surrounding most of those instances.

When God sent the flood of Noah’s day.

God told Noah that He would “cause it to rain on the earth forty days and forty nights” (Genesis 7:4). It happened exactly as God said.

And the rain was on the earth forty days and forty nights. (Genesis 7:12)

While the flood is a story of God’s righteous judgment upon sin (Genesis 6:5-7), it is also a record of God’s grace and mercy upon the faithful (Genesis 6:8; 8:1).

When God met with Moses at Mt. Sinai.

God called Moses to come up to Mt. Sinai so He could give Moses the “tablets of stone, and the law and the commandments” (Exodus 24:12). Moses remained on the mountain “forty days and forty nights” (Exodus 24:18).

Moses had to return to receive the tablets again after he threw the first ones down on the ground when he saw the golden calf Israel was worshipping (Exodus 32:19). He stayed on the mountain with the LORD another “forty days and forty nights” (Exodus 34:28), and fasted.

Moses receiving the law from God points to God’s righteousness but also shows Israel’s sin in immediately breaking God’s law. His mercy and grace are demonstrated in renewing His covenant with Israel (Exodus 34:6-28).

When Goliath threatened Israel.

Goliath defied the armies of Israel for forty days, morning and night (1 Samuel 17:16). In reality, he defied the armies of the living God (1 Samuel 17:26). God delivered His people through David - the only one who trusted the promises and power of God (1 Samuel 17:45-47).

The Lord delivered His people from their enemies at the end of those forty days and nights. His power and protection of His people and His ability to keep His promises are demonstrated in 1 Samuel 17.

When Elijah fasted as he traveled to Horeb.

Elijah ran into the wilderness to protect his life from Jezebel and wished for the Lord to take his life (1 Kings 19:1-4). God was merciful to him, protected Elijah, and fed him (1 Kings 19:5-7). Elijah traveled to Horeb for “forty days and forty nights” by the strength that food gave him (1 Kings 19:8).

Interestingly, Mt. Horeb and Mt. Sinai are thought to be two different names for the same place.

When God commanded Ezekiel to lie on his right side.

Ezekiel became a living illustration of one who would “bear the iniquity” of Israel.

And when you have completed them, lie again on your right side; then you shall bear the iniquity of the house of Judah forty days. I have laid on you a day for each year. (Ezekiel 4:6)

In this instance, forty days pointed to the sin of God’s people but also to one who would “bear” their sins.

When Jonah preached to the city of Nineveh.

When Jonah finally decided to obey God and go to Nineveh, he proclaimed God's message.

And Jonah began to enter the city on the first day’s walk. Then he cried out and said, “Yet forty days, and Nineveh shall be overthrown!” (Jonah 3:4)

The people of Nineveh repented at the preaching of Jonah, and God “relented from the disaster that He had said He would bring upon them, and He did not do it” (Jonah 3:10).

Again in connection with “forty days,” we find this same theme of God’s righteous judgment upon sin and His mercy and grace shown to those who are faithful to Him or who repent of their sin.

The time Jesus fasted in the wilderness.

We find “forty days and forty nights” at the beginning of Jesus’ earthly ministry.

Then Jesus was led up by the Spirit into the wilderness to be tempted by the devil. And when He had fasted forty days and forty nights, afterward He was hungry. (Matthew 4:1-2)

After Jesus resisted all the temptations of the devil, He began preaching, “Repent, for the kingdom of heaven is at hand” (Matthew 4:17).

He came as the one on which the Lord would lay all our iniquity (Isaiah 53:6).

Connecting the themes from the “40-day” references to Jesus.

Some major themes that are emphasized throughout all the passages we’ve noticed are:

• God’s righteous judgment upon sin and the high price that sin brings.

• God’s grace and mercy extended to all who will turn to Him.

• God’s willingness and ability to keep His promises and protect His people.

And we find all these themes wrapped up in Jesus Christ - the Son of God.

• The righteous judgment of God required a price be paid for sin - and the price was paid was the blood of Jesus (2 Corinthians 5:21; Romans 5:6-9; 1 Peter 2:21-25).

• God’s grace and mercy are extended to all people through Jesus Christ (Titus 2:11-14; 1 Timothy 1:12-17).

• Through Jesus Christ, God keeps His promises and protects His own people (John 10:27-30; Hebrews 11:13-16; 12:1-2).

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