The most important event in the Bible is Jesus resurrection. That he died in the cross and on the third day, he was ressurected by God the Father. In the first century, christians used the symbol of the fish to identify themselves and to confirm their identity when meeting strangers.
Jonas was a representation of Jesus resurrection.  Inside the belly of the whale for three days, and coming out alive.
Believers in the early church drew one half arc of the fish as a signal when meeting across the roman empire. If the stranger completed the other half arc, forming the figure of a fish, then each other was assured that they were believers IN CHRIST, who died and resurrected on the third day. These early christians were primarily jewish, and they travelled far and beyond the known roman and greek world they called Asia. The message was simple but life changing, that God the Father no longer saw them as enemies, but now through Jesus, our lord and saviour he saw us as his children. Co-Heirs with the Son Of The Living God, if we simply believe IN HIM who died and was ressurected from the dead. Can you imagine how these first disciples of Christ carried the Gospel as they visited sinagogues and confronted the the people of the land of Israel and beyond? Let’s read about them, please clic the following link:
La Raíz Del Olivo