What is the sign of Jonah?

Question: "What is the sign of Jonah?" 

https://www.gotquestions.org/sign-of-Jonah.html

 ( Note: ...Jonah was soon thrown overboard and swallowed by a great fish where he remained for “three days and three nights” (Jonah 1:15–17). After the three-day period, the Lord caused the great fish to vomit Jonah out onto dry land (Jonah 2:10).)

Answer: The phrase “sign of Jonah” was used by Jesus as a typological metaphor for His future crucifixion, burial, and resurrection. Jesus answered with this expression when asked by the Pharisees for miraculous proof the He was indeed the Messiah. The Pharisees remained unconvinced of Jesus’ claims about Himself, despite His having just cured a demon-possessed man who was both blind and mute. Shortly after the Pharisees accused Jesus of driving out demons by the power of Satan, they said to Him, “Teacher, we want to see a sign from you.” He answered, “A wicked and adulterous generation asks for a sign! But none will be given it except the sign of the prophet Jonah. For as Jonah was three days and three nights in the belly of a huge fish, so the Son of Man will be three days and three nights in the heart of the earth. The men of Nineveh will stand up at the judgment with this generation and condemn it; for they repented at the preaching of Jonah, and now something greater than Jonah is here” (Matthew 12:38–41).

To fully appreciate the answer that Jesus gave, we must go to the Old Testament book of Jonah. In its first chapter, we read that God commanded the prophet Jonah to go to the city of Nineveh and warn its people that He was going to destroy it for its wickedness. Jonah disobediently ran from the Lord and headed for the city of Tarshish by boat. The Lord then sent a severe storm that caused the crew of the ship to fear for their lives. Jonah was soon thrown overboard and swallowed by a great fish where he remained for “three days and three nights” (Jonah 1:15–17). After the three-day period, the Lord caused the great fish to vomit Jonah out onto dry land (Jonah 2:10).

It is this three days that Jesus was referring to when He spoke of the sign of Jonah. Jesus had already been producing miracles that were witnessed by many. Jesus had just performed a great sign in the Pharisees’ presence by healing a deaf man who was possessed of a demon. Rather than believe, they accused Jesus of doing this by the power of Satan. Jesus recognized their hardness of heart and refused to give them further proof of His identity. However, He did say that there would be one further sign forthcoming, His resurrection from the dead. This would be their final opportunity to be convinced.

Jesus’ paralleling of the Pharisees with the people of Nineveh is telling. The people of Nineveh repented of their evil ways (Jonah 3:4–10) after hearing Jonah’s call for repentance, while the Pharisees continued in their unbelief despite being eyewitnesses to the miracles of Jesus. Jesus was telling the Pharisees that they were culpable for their unbelief, given the conversion of the people of Nineveh, sinners who had received far less evidence than the Pharisees themselves had witnessed.

But what are we to make of the phrase “three days and three nights”? Was Jesus saying that He would be dead for three full 24-hour periods before He would rise from the dead? It does not appear so. The phrase “three days and three nights” need not refer to a literal 72-hour period. Rather, according to the Hebrew reckoning of time, the days could refer to three days in part or in whole. Jesus was probably crucified on a Friday (Mark 15:42). According to the standard reckoning, Jesus died at about 3:00 PM (Matthew 27:46) on Friday (day 1). He remained dead for all of Saturday (day 2) and rose from the dead early on Sunday morning (day 3). Attempts to place Jesus’ death on Wednesday to accommodate a literal 72-hour period are probably unnecessary once we take into account the Hebrew method of reckoning of each day as beginning at sundown. So it seems that the expression “three days and three nights” was used as a figure of speech meant to signify any part of three days.

God would often use signs (or miracles) in the Bible to authenticate His chosen messenger. The Lord provided Moses with several miraculous signs in order to prove to others that he was appointed by God (Exodus 4:5–9; 7:8–10;19-20). God sent down fire on Elijah’s altar during Elijah’s contest with the prophets of Baal (1 Kings 18:36–39). He performed this miracle to prove that the God of Israel was the one true God. Jesus Himself would perform many miracles (or “signs”) to demonstrate His power over nature (Matthew 4:23; Mark 6:30–44; Luke 8:22–24; John 6:16–24). The “sign of Jonah” would turn out to be Jesus’ greatest miracle of all. Jesus’ resurrection from the dead would be God’s chief sign that Jesus was Israel’s long-awaited Messiah (Acts 2:23–32) and establish Christ’s claims to deity (Romans 1:3–4).