We are in the month of Adar. The Talmud says: “When Adar enters, we increase joy” (b.Ta'anit 29a).
Adar is the month in which we observe the joyous festival of Purim and the symbol for the month of Adar is the fish. What do fish have to do with Adar and Purim? In Jewish mysticism the fish represents a concealed reality. This is because the fish swims under the water and is hidden from plain sight. The book of Esther is full of concealed realities. For example the Jewish identity of Esther and Mordecai is hidden from the king and Haman. God himself and his hand are concealed throughout the story, so much so that he is not even mentioned in the book. He is certainly working but it is behind the scenes, so to speak.
The fish is also an appropriate symbol for the Jewish people. Their true identity and spiritual inheritance is hidden from most of the people of the world. The nations do not realize that if they bless Israel they will be blessed and if they curse them they will be cursed. They also do not realize that Israel is destined to rule over the whole world. Rashi commenting on Jacob’s blessing, “Let them grow into a multitude [like fish] in the midst of the earth” (Genesis 48:16), writes: “[Just] like fish, which proliferate and multiply, and are unaffected by the evil eye.” Rabbi Akiva likens the Jewish people to fish and the Torah to the water they swim in; just as a fish cannot live without water, the Jewish people cannot live without Torah (b.Brachot 61b).
For us as believers when we think of the symbol of the fish, probably what most likely comes to mind is the Christian fish symbol of the Ichthus. Ichthus is the Greek word for fish and is said to have been used in the early church as an acrostic for “Jesus Christ God’s Son Savior.” It already appears in conjunction with Christianity in the artwork of the mid-third-century catacombs of Rome and quite possibly it was used earlier as well. According to popular Christian tradition the symbol was a means whereby two disciples could identify one another during a time of heavy persecution from the Romans. As two strangers met, one would make an arc in the dirt forming one half of the fish, if the other completed the symbol, they recognized each other as disciples of Yeshua.
The fish symbol seems like a natural fit for the early believers. Many of the disciples were fishermen, there are many fish stories in the Gospels such as the feeding of the five thousand and the story of the miraculous catch of fish, and we have the Master’s words to the disciples that they will be “fishers of men.” There are some scholars that even believe it was used by Judaism before the time of Yeshua and was thus subsequently adopted by believers.
Gedaliahu Stroumsa feels that it is related to Yehoshua ben Nun, Joshua son of Nun.  There is a close semantic proximity between Joshua and Yeshua. Yeshua is the shortened Aramaic version of the Hebrew Yehoshua. Add onto that that in Aramaic, the word Nun means “fish” and you have the association of both Joshua and Yeshua with a fish. The Midrash Rabbah reads:
And the son of him whose name was as the name of a fish would lead them into the land: Nun his son, Joshua his son.
Therefore in light of the background of the legends that associated Joshua with a fish, Strousma believes it would be natural for Yeshua to be associated a fish symbol as well. Breslov tradition holds that one of the names of Messiah is Dag ("Fish")
Returning to the theme of concealment, Messiah is currently hidden from the world. He revealed himself in his first coming but was henceforth concealed until he returns once again and ushers in the Messianic Era. The kingdom of heaven is at hand but is also concealed to most people. But Messiah and his kingdom are not concealed to us as his followers. We can partake in a taste of that kingdom now as we eagerly await the day it will arrive in its fullness. In this way the story of Purim prefigures the story of redemption: What is hidden now will soon be revealed. For now let us all experience the increased joy of Adar and eat some extra fish this month as we long for the day that the concealment ends and the whole world will know who the King is and experience his kingdom.
- Gedaliahu G. Stroumsa, “The Early Christian Fish Symbol Reconsidered,” in Messiah and Christos: Studies in the Jewish Origins of Christianity (ed. Ithamar Gruenwald, Shaul Shaked, and Gedaliahu G. Stroumsa; TÃ¼bingen, Germany: J.C.B. Mohr, 1992), 199-205.
- Rebbe Nachman, Likkutei Moharan 2:8.